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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-Q

 

(Mark One)

☒			QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the quarterly period ended September 30, 2020

OR

☐			TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the transition period from ______ to ______

Commission File No. 1-6571

Merck & Co., Inc.

(Exact name of registrant as specified in its charter)

New Jersey			22-1918501
(State or other jurisdiction of incorporation)			(I.R.S Employer Identification No.)
2000 Galloping Hill Road
Kenilworth			New Jersey			07033
(Address of principal executive offices) (zip code)

(Registrant’s telephone number, including area code) (908) 740-4000

			Not Applicable
(Former name, former address and former fiscal year, if changed since last report.)

Indicate by check mark whether the registrant: (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.  Yes  ☒   No  ☐

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files).  Yes  ☒   No  ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act. (Check one):

Large accelerated filer			☒			Accelerated filer			☐
Non-accelerated filer			☐			Smaller reporting company			☐
						Emerging growth company			☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).  Yes ☐  No ☒

Securities Registered pursuant to Section 12(b) of the Act:
Title of each class			Trading Symbol(s)			Name of each exchange on which registered
Common Stock ($0.50 par value)			MRK			New York Stock Exchange
1.125% Notes due 2021			MRK/21			New York Stock Exchange
0.500% Notes due 2024			MRK 24			New York Stock Exchange
1.875% Notes due 2026			MRK/26			New York Stock Exchange
2.500% Notes due 2034			MRK/34			New York Stock Exchange
1.375% Notes due 2036			MRK 36A			New York Stock Exchange

The number of shares of common stock outstanding as of the close of business on October 31, 2020: 2,530,034,437

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Table of Contents

Page No.

PART I

FINANCIAL INFORMATION

3

Item 1.

Financial Statements

3

Condensed Consolidated Statement of Income

3

Condensed Consolidated Statement of Comprehensive Income

3

Condensed Consolidated Balance Sheet

4

Condensed Consolidated Statement of Cash Flows

5

Notes to Condensed Consolidated Financial Statements

6

Item 2.

Management’s Discussion and Analysis of Financial Condition and Results of Operations

33

Item 4.

Controls and Procedures

51

Cautionary Factors That May Affect Future Results

51

PART II

OTHER INFORMATION

51

Item 1.

Legal Proceedings

51

Item 1A.

Risk Factors

51

Item 2.

Unregistered Sales of Equity Securities and Use of Proceeds

52

Item 6.

Exhibits

53

Signatures

54

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Part I - Financial Information

Item 1. Financial Statements

MERCK & CO., INC. AND SUBSIDIARIES

CONDENSED CONSOLIDATED STATEMENT OF INCOME

(Unaudited, $ in millions except per share amounts)

 

			Three Months Ended September 30,												Nine Months Ended September 30,
			2020						2019						2020						2019
Sales			$	12,551					$	12,397					$	35,479					$	34,972
Costs, Expenses and Other
Cost of sales			3,481						3,990						9,952						10,443
Selling, general and administrative			2,450						2,589						7,383						7,726
Research and development			3,390						3,204						7,721						7,324
Restructuring costs			114						232						269						444
Other (income) expense, net			(312)						35						(630)						362
			9,123						10,050						24,695						26,299
Income Before Taxes			3,428						2,347						10,784						8,673
Taxes on Income			483						440						1,611						1,259
Net Income			2,945						1,907						9,173						7,414
Less: Net Income (Loss) Attributable to Noncontrolling Interests			4						6						12						(73)
Net Income Attributable to Merck & Co., Inc.			$	2,941					$	1,901					$	9,161					$	7,487
Basic Earnings per Common Share Attributable to Merck & Co., Inc. Common Shareholders			$	1.16					$	0.74					$	3.62					$	2.91
Earnings per Common Share Assuming Dilution Attributable to Merck & Co., Inc. Common Shareholders			$	1.16					$	0.74					$	3.61					$	2.89

 

MERCK & CO., INC. AND SUBSIDIARIES

CONDENSED CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME

(Unaudited, $ in millions)

 

			Three Months Ended September 30,												Nine Months Ended September 30,
			2020						2019						2020						2019
Net Income Attributable to Merck & Co., Inc.			$	2,941					$	1,901					$	9,161					$	7,487
Other Comprehensive Income (Loss) Net of Taxes:
Net unrealized (loss) gain on derivatives, net of reclassifications			(137)						91						(153)						(9)
Net unrealized (loss) gain on investments, net of reclassifications			—						(17)						(18)						109
Benefit plan net gain and prior service credit, net of amortization			62						15						161						41
Cumulative translation adjustment			85						(117)						(180)						14
			10						(28)						(190)						155
Comprehensive Income Attributable to Merck & Co., Inc.			$	2,951					$	1,873					$	8,971					$	7,642

 The accompanying notes are an integral part of these condensed consolidated financial statements.

- 3 -

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MERCK & CO., INC. AND SUBSIDIARIES

CONDENSED CONSOLIDATED BALANCE SHEET

(Unaudited, $ in millions except per share amounts)

 

			September 30, 2020						December 31, 2019
Assets
Current Assets
Cash and cash equivalents			$	7,356					$	9,676
Short-term investments			—						774
Accounts receivable (net of allowance for doubtful accounts of $89 in 2020  and $86 in 2019)			8,422						6,778
Inventories (excludes inventories of $2,081 in 2020 and $1,480 in 2019 classified in Other assets - see Note 6)			6,128						5,978
Other current assets			4,671						4,277
Total current assets			26,577						27,483
Investments			1,372						1,469
Property, Plant and Equipment, at cost, net of accumulated depreciation of $18,572 in 2020 and $17,686 in 2019			16,919						15,053
Goodwill			20,248						19,425
Other Intangibles, Net			16,677						14,196
Other Assets			8,007						6,771
			$	89,800					$	84,397
Liabilities and Equity
Current Liabilities
Loans payable and current portion of long-term debt			$	2,420					$	3,610
Trade accounts payable			3,744						3,738
Accrued and other current liabilities			11,690						12,549
Income taxes payable			984						736
Dividends payable			1,567						1,587
Total current liabilities			20,405						22,220
Long-Term Debt			26,321						22,736
Deferred Income Taxes			1,777						1,470
Other Noncurrent Liabilities			12,027						11,970
Merck & Co., Inc. Stockholders’ Equity
Common stock, $0.50 par value Authorized - 6,500,000,000 shares Issued - 3,577,103,522 shares in 2020 and 2019			1,788						1,788
Other paid-in capital			39,489						39,660
Retained earnings			51,107						46,602
Accumulated other comprehensive loss			(6,383)						(6,193)
			86,001						81,857
Less treasury stock, at cost: 1,047,343,390 shares in 2020 and 1,038,087,496 shares in 2019			56,815						55,950
Total Merck & Co., Inc. stockholders’ equity			29,186						25,907
Noncontrolling Interests			84						94
Total equity			29,270						26,001
			$	89,800					$	84,397

The accompanying notes are an integral part of this condensed consolidated financial statement.

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MERCK & CO., INC. AND SUBSIDIARIES

CONDENSED CONSOLIDATED STATEMENT OF CASH FLOWS

(Unaudited, $ in millions)

 

			Nine Months Ended September 30,
			2020						2019
Cash Flows from Operating Activities
Net income			$	9,173					$	7,414
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization			2,721						2,716
Intangible asset impairment charges			35						864
Charge for acquisition of Peloton Therapeutics, Inc.			—						982
Deferred income taxes			47						(386)
Share-based compensation			354						306
Other			(445)						219
Net changes in assets and liabilities			(5,638)						(3,469)
Net Cash Provided by Operating Activities			6,247						8,646
Cash Flows from Investing Activities
Capital expenditures			(3,170)						(2,336)
Purchases of securities and other investments			(78)						(2,380)
Proceeds from sales of securities and other investments			1,894						7,459
Acquisition of ArQule, Inc., net of cash acquired			(2,545)						—
Acquisition of Antelliq Corporation, net of cash acquired			—						(3,620)
Acquisition of Peloton Therapeutics, Inc., net of cash acquired			—						(1,040)
Other acquisitions, net of cash acquired			(907)						(269)
Other			141						320
Net Cash Used in Investing Activities			(4,665)						(1,866)
Cash Flows from Financing Activities
Net change in short-term borrowings			(311)						(3,892)
Payments on debt			(1,954)						—
Proceeds from issuance of debt			4,419						4,958
Purchases of treasury stock			(1,281)						(3,730)
Dividends paid to stockholders			(4,673)						(4,290)
Proceeds from exercise of stock options			68						344
Other			(472)						(240)
Net Cash Used in Financing Activities			(4,204)						(6,850)
Effect of Exchange Rate Changes on Cash, Cash Equivalents and Restricted Cash			89						(26)
Net Decrease in Cash, Cash Equivalents and Restricted Cash			(2,533)						(96)
Cash, Cash Equivalents and Restricted Cash at Beginning of Year (includes restricted cash of $258 at January 1, 2020 included in Other Assets)			9,934						7,967
Cash, Cash Equivalents and Restricted Cash at End of Period (includes restricted cash of $45 at September 30, 2020 included in Other Assets)			$	7,401					$	7,871

The accompanying notes are an integral part of this condensed consolidated financial statement.

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Notes to Condensed Consolidated Financial Statements (unaudited)

1.Basis of Presentation

The accompanying unaudited condensed consolidated financial statements of Merck & Co., Inc. (Merck or the Company) have been prepared pursuant to the rules and regulations for reporting on Form 10-Q. Accordingly, certain information and disclosures required by accounting principles generally accepted in the United States (GAAP) for complete consolidated financial statements are not included herein. These interim statements should be read in conjunction with the audited financial statements and notes thereto included in Merck’s Form 10-K filed on February 26, 2020.

The results of operations of any interim period are not necessarily indicative of the results of operations for the full year. In the Company’s opinion, all adjustments necessary for a fair statement of these interim statements have been included and are of a normal and recurring nature.

Planned Spin-Off of Women’s Health, Biosimilars and Established Brands into New Company

In February 2020, Merck announced its intention to spin-off products from its women’s health, biosimilars and established brands businesses into a new, independent, publicly traded company named Organon & Co. (Organon) through a distribution of Organon’s publicly traded stock to Company shareholders. The distribution is expected to qualify as tax-free to the Company and its shareholders for U.S. federal income tax purposes. The established brands included in the transaction consist of dermatology, non-opioid pain management, respiratory, and select cardiovascular products including Zetia (ezetimibe) and Vytorin (ezetimibe and simvastatin), as well as the rest of Merck’s diversified brands franchise. Merck’s existing research pipeline programs will continue to be owned and developed within Merck as planned. Organon will have development capabilities initially focused on late-stage development and life-cycle management and is expected over time to develop research capabilities in selected therapeutic areas. The spin-off is expected to be completed in the second quarter of 2021, subject to market and certain other conditions. Subsequent to the spin-off, the historical results of the women’s health, biosimilars and established brands businesses will be reflected as discontinued operations in the Company’s consolidated financial statements.

Recently Adopted Accounting Standards

In June 2016, the Financial Accounting Standards Board (FASB) issued new guidance on the accounting for credit losses on financial instruments. The new guidance introduces an expected loss model for estimating credit losses, replacing the incurred loss model. The new guidance also changes the impairment model for available-for-sale debt securities, requiring the use of an allowance to record estimated credit losses (and subsequent recoveries). The Company adopted the new guidance effective January 1, 2020. There was no impact to the Company’s consolidated financial statements upon adoption.

In November 2018, the FASB issued new guidance for collaborative arrangements intended to reduce diversity in practice by clarifying whether certain transactions between collaborative arrangement participants should be accounted for under revenue recognition guidance (ASC 606). The Company adopted the new guidance effective January 1, 2020, which resulted in minor changes to the presentation of information related to the Company’s collaborative arrangements.

Recently Issued Accounting Standards Not Yet Adopted

In December 2019, the FASB issued amended guidance on the accounting and reporting of income taxes. The guidance is intended to simplify the accounting for income taxes by: removing exceptions related to certain intraperiod tax allocations and deferred tax liabilities; clarifying guidance primarily related to evaluating the step-up tax basis for goodwill in a business combination; and reflecting enacted changes in tax laws or rates in the annual effective tax rate. The amended guidance is effective for interim and annual periods in 2021. Early adoption is permitted. The amendments in the new guidance are to be applied on a retrospective basis, on a modified retrospective basis through a cumulative-effect adjustment to retained earnings or prospectively, depending on the amendment. The Company is currently evaluating the impact of adoption on its consolidated financial statements.

In January 2020, the FASB issued new guidance intended to clarify certain interactions between accounting standards related to equity securities, equity method investments and certain derivatives. The guidance addresses accounting for the transition into and out of the equity method of accounting and measuring certain purchased options and forward contracts to acquire investments. The new guidance is effective for interim and annual periods in 2021 and is to be applied prospectively. Early adoption is permitted. The Company is currently evaluating the impact of adoption on its consolidated financial statements.

In March 2020, the FASB issued optional guidance to ease the potential burden in accounting for (or recognizing the effects of) reference rate reform on financial reporting. The guidance provides optional expedients and exceptions for applying GAAP to contracts, hedging relationships, and other transactions affected by reference rate reform. The optional guidance is effective upon issuance and can be applied on a prospective basis at any time between January 1, 2020 through December 31, 2022. The Company is currently evaluating the impact of adoption on its consolidated financial statements.

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Notes to Condensed Consolidated Financial Statements (unaudited) (continued)

2.    Acquisitions, Research Collaborations and License Agreements

The Company continues to pursue acquisitions and the establishment of external alliances such as research collaborations and licensing agreements to complement its internal research capabilities. These arrangements often include upfront payments, as well as expense reimbursements or payments to the third party, and milestone, royalty or profit share arrangements, contingent upon the occurrence of certain future events linked to the success of the asset in development. The Company also reviews its marketed products and pipeline to examine candidates which may provide more value through out-licensing and, as part of its portfolio assessment process, may also divest certain assets. Pro forma financial information for acquired businesses is not presented if the historical financial results of the acquired entity are not significant when compared with the Company’s financial results.

In November 2020, Merck and VelosBio, Inc. (VelosBio) announced that the companies had entered into a definitive agreement pursuant to which Merck, through a subsidiary, will acquire all outstanding shares of VelosBio for $2.75 billion, subject to certain customary adjustments. VelosBio is a privately held clinical-stage biopharmaceutical company committed to developing first-in-class cancer therapies targeting receptor tyrosine kinase-like orphan receptor 1 (ROR1). VelosBio’s lead investigational candidate is VLS-101, an antibody-drug conjugate targeting ROR1 that is currently being evaluated in a Phase 1 and a Phase 2 clinical trial for the treatment of patients with hematologic malignancies and solid tumors, respectively. The closing of the transaction, which is subject to approval under the Hart-Scott-Rodino Antitrust Improvements Act and other customary conditions, is expected by the end of 2020.

In September 2020, Merck and Seagen Inc. (Seagen, formerly known as Seattle Genetics, Inc.) announced an oncology collaboration to globally develop and commercialize Seagen’s ladiratuzumab vedotin (MK-6440), an investigational antibody-drug conjugate targeting LIV-1, which is currently in Phase 2 clinical trials for breast cancer and other solid tumors. The collaboration will pursue a broad joint development program evaluating ladiratuzumab vedotin as monotherapy and in combination with Keytruda (pembrolizumab) in triple-negative breast cancer, hormone receptor-positive breast cancer and other LIV-1-expressing solid tumors. The companies will equally share profits worldwide. Under the terms of the agreement, Merck made an upfront payment of $600 million and a $1.0 billion equity investment in 5 million shares of Seagen common stock at a price of $200 per share. Merck recorded $622 million in Research and development expenses in the third quarter and first nine months of 2020 related to this transaction reflecting the upfront payment as well as a $22 million mark-to-market loss on the purchase commitment (forward contract) relating to the equity shares (calculated based on the closing price of Seagen common stock on September 30, 2020). The closing of the equity investment occurred in October 2020 and resulted in the recognition of a $6 million reduction to Research and development expenses based on the price of Seagen common stock on the closing date. Seagen is also eligible to receive future contingent milestone payments of up to $2.6 billion, including $850 million in development milestones and $1.75 billion in sales milestones.

Concurrent with the above transaction, Seagen granted Merck an exclusive license to commercialize Tukysa (tucatinib), a small molecule tyrosine kinase inhibitor, for the treatment of HER2-positive cancers, in Asia, the Middle East and Latin America and other regions outside of the United States, Canada and Europe. Merck will be responsible for marketing applications seeking approval in its territories, supported by the positive results from the HER2CLIMB clinical trial. Merck will also co-fund a portion of the Tukysa global development plan, which encompasses several ongoing and planned trials across HER2-positive cancers, including breast, colorectal, gastric and other cancers set forth in a global product development plan. Merck will solely fund and conduct country-specific clinical trials necessary to support anticipated regulatory applications in its territories. Under the terms of the agreement, Merck made upfront payments aggregating $210 million, which were recorded as Research and development expenses in the third quarter and first nine months of 2020. Seagen is also eligible to receive future contingent regulatory approval milestones of up to $65 million and will receive tiered royalties ranging from 20% to 33% based on annual sales levels of Tukysa in Merck’s territories.

Additionally in September 2020, Merck acquired a biologics manufacturing facility located in Dunboyne, Ireland from Takeda Pharmaceutical Company Limited for €256 million ($302 million). The transaction was accounted for as an acquisition of an asset. Merck recorded property, plant and equipment of $289 million and other net assets of $13 million. There are no future contingent payments associated with the acquisition.

In July 2020, Merck acquired the U.S. rights to Sentinel Flavor Tabs and Sentinel Spectrum Chews from Virbac Corporation for $410 million. Sentinel products provide protection against common parasites in dogs. The transaction was accounted for as an acquisition of an asset. Merck recognized intangible assets of $401 million related to currently marketed products and inventory of $9 million at the acquisition date. The estimated fair values of the identifiable intangible assets related to currently marketed products were determined using an income approach. Actual cash flows are likely to be different than those assumed. The intangible assets related to currently marketed products will be amortized over their estimated useful lives of 15 years. There are no future contingent payments associated with the acquisition.

Also, in July 2020, Merck and Ridgeback Biotherapeutics LP (Ridgeback Bio), a closely held biotechnology company, closed a collaboration agreement to develop molnupiravir (MK-4482, formerly known as EIDD-2801), an orally

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Notes to Condensed Consolidated Financial Statements (unaudited) (continued)

available antiviral candidate currently in clinical development for the treatment of patients with COVID-19. Merck gained exclusive worldwide rights to develop and commercialize molnupiravir and related molecules. Under the terms of the agreement, Ridgeback Bio received an upfront payment and also is eligible to receive future contingent payments dependent upon the achievement of certain developmental and regulatory approval milestones, as well as a share of the net profits of molnupiravir and related molecules, if approved. Merck and Ridgeback are committed to ensure that any medicines developed for SARS-CoV-2 (the causative agent of COVID-19) will be accessible and affordable globally.

In June 2020, Merck acquired privately held Themis Bioscience GmbH (Themis), a company focused on vaccines and immune-modulation therapies for infectious diseases and cancer for $366 million. Merck may make additional contingent payments of up to $740 million, including up to $80 million for development milestones, up to $260 million for regulatory approval milestones, and up to $400 million for commercial milestones. Themis has a broad pipeline of vaccine candidates and immune-modulatory therapies developed using its innovative measles virus vector platform based on a vector originally developed by scientists at the Institut Pasteur and licensed exclusively to Themis for select viral indications. The acquisition builds upon an ongoing collaboration between the two companies to develop vaccine candidates using the measles virus vector platform and is expected to accelerate the development of the COVID-19 vaccine candidate (V591), which is currently in Phase 1 clinical development. The transaction was accounted for as an acquisition of a business. The Company determined the fair value of the contingent consideration was $97 million at the acquisition date utilizing a probability-weighted estimated cash flow stream using an appropriate discount rate dependent on the nature and timing of the milestone payment. Merck recognized intangible assets for in-process research and development (IPR&D) of $136 million, cash of $59 million, deferred tax assets of $71 million and other net liabilities of $32 million. The excess of the consideration transferred over the fair value of net assets acquired of $229 million was recorded as goodwill that was allocated to the Pharmaceutical segment and is not deductible for tax purposes. The fair values of the identifiable intangible assets related to IPR&D were determined using an income approach. Actual cash flows are likely to be different than those assumed. In connection with the transaction, Merck has entered into a memorandum of understanding that reflects the parties’ commitments to address the COVID-19 pandemic by developing, manufacturing and distributing the vaccine on a global basis and with pricing that makes the vaccine both available around the world and accessible to those who need it.

In May 2020, Merck and the International AIDS Vaccine Initiative, Inc. (IAVI), a nonprofit scientific research organization dedicated to addressing urgent, unmet global health challenges, announced a new collaboration to develop V590, an investigational vaccine against SARS-CoV-2 being studied for the prevention of COVID-19. This vaccine candidate will use the recombinant vesicular stomatitis virus (rVSV) technology that is the basis for Merck’s approved Ebola Zaire virus vaccine, Ervebo (Ebola Zaire Vaccine, Live), which was the first rVSV vaccine approved for use in humans. Under the terms of the agreement, Merck made an upfront payment of $6.5 million and may make additional contingent payments of up to $100 million for sales-based milestones, as well as royalty payments. Merck has also signed an agreement with the Biomedical Advanced Research and Development Authority (BARDA), part of the office of the Assistant Secretary for Preparedness and Response within an agency of the United States Department of Health and Human Services, to provide initial funding support for this effort. Under the agreement, IAVI and Merck will work together to advance the development and global clinical evaluation of a SARS-CoV-2 vaccine candidate designed and engineered by IAVI scientists. The vaccine candidate is currently in Phase 1 clinical development. Merck will lead regulatory filings globally. Both organizations will work together to develop the vaccine and make it accessible and affordable globally, if approved.

In January 2020, Merck acquired ArQule, Inc. (ArQule), a publicly traded biopharmaceutical company focused on kinase inhibitor discovery and development for the treatment of patients with cancer and other diseases. Total consideration paid of $2.7 billion included $138 million of share-based compensation payments to settle equity awards attributable to precombination service and cash paid for transaction costs on behalf of ArQule. The Company incurred $95 million of transaction costs directly related to the acquisition of ArQule, consisting almost entirely of share-based compensation payments to settle non-vested equity awards attributable to postcombination service. These costs were included in Selling, general and administrative expenses in the first nine months of 2020. ArQule’s lead investigational candidate, MK-1026 (formerly known as ARQ 531), is a novel, oral Bruton’s tyrosine kinase (BTK) inhibitor currently being evaluated for the treatment of B-cell malignancies.

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Notes to Condensed Consolidated Financial Statements (unaudited) (continued)

The estimated fair value of assets acquired and liabilities assumed from ArQule is as follows:

($ in millions)			January 16, 2020
Cash and cash equivalents			$	145
IPR&D MK-1026 (formerly ARQ 531) (1)			2,280
Licensing arrangement for ARQ 087			80
Deferred income tax liabilities			(389)
Other assets and liabilities, net			34
Total identifiable net assets			2,150
Goodwill (2)			540
Consideration transferred			$	2,690

(1)    The estimated fair value of the identifiable intangible asset related to IPR&D was determined using an income approach. The future net cash flows were discounted to present value utilizing a discount rate of 12.5%. Actual cash flows are likely to be different than those assumed.

(2)    The goodwill was allocated to the Pharmaceutical segment and is not deductible for tax purposes.

In July 2019, Merck acquired Peloton Therapeutics, Inc. (Peloton), a clinical-stage biopharmaceutical company focused on the development of novel small molecule therapeutic candidates targeting hypoxia-inducible factor-2α (HIF-2α) for the treatment of patients with cancer and other non-oncology diseases. Peloton’s lead candidate, MK-6482 (formerly known as PT2977), is a novel investigational oral HIF-2α inhibitor in late-stage development for renal cell carcinoma. Merck made an upfront payment of $1.2 billion; additionally, former Peloton shareholders will be eligible to receive $50 million upon U.S. regulatory approval, $50 million upon first commercial sale in the United States, and up to $1.05 billion of sales-based milestones. The transaction was accounted for as an acquisition of an asset. Merck recorded cash of $157 million, deferred tax liabilities of $64 million, and other net liabilities of $6 million at the acquisition date and Research and development expenses of $982 million in the third quarter and first nine months of 2019 related to the transaction.

On April 1, 2019, Merck acquired Antelliq Corporation (Antelliq), a leader in digital animal identification, traceability and monitoring solutions. These solutions help veterinarians, farmers and pet owners gather critical data to improve management, health and well-being of livestock and pets. Merck paid $2.3 billion to acquire all outstanding shares of Antelliq and spent $1.3 billion to repay Antelliq’s debt. The transaction was accounted for as an acquisition of a business.

The estimated fair value of assets acquired and liabilities assumed from Antelliq is as follows:

($ in millions)			April 1, 2019
Cash and cash equivalents			$	31
Accounts receivable			73
Inventories			93
Property, plant and equipment			60
Identifiable intangible assets (useful lives ranging from 18-24 years) (1)			2,689
Deferred income tax liabilities			(589)
Other assets and liabilities, net			(82)
Total identifiable net assets			2,275
Goodwill (2)			1,376
Consideration transferred			$	3,651

(1)    The estimated fair values of identifiable intangible assets relate primarily to trade names and were determined using an income approach. The future net cash flows were discounted to present value utilizing a discount rate of 11.5%. Actual cash flows are likely to be different than those assumed.

(2)    The goodwill recognized is largely attributable to anticipated synergies expected to arise after the acquisition and was allocated to the Animal Health segment. The goodwill is not deductible for tax purposes.

The Company’s results for the first nine months of 2019 include five months of activity for Antelliq. The Company incurred $47 million of transaction costs directly related to the acquisition of Antelliq, consisting largely of advisory fees, which are reflected in Selling, general and administrative expenses in the first nine months of 2019.

Also in April 2019, Merck acquired Immune Design, a late-stage immunotherapy company employing next-generation in vivo approaches to enable the body’s immune system to fight disease, for $301 million in cash. The transaction was accounted for as an acquisition of a business. Merck recognized intangible assets of $156 million, cash of $83 million and other net assets of $42 million. The excess of the consideration transferred over the fair value of net assets acquired of $20

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Notes to Condensed Consolidated Financial Statements (unaudited) (continued)

million was recorded as goodwill that was allocated to the Pharmaceutical segment and is not deductible for tax purposes. The fair values of the identifiable intangible assets related to IPR&D were determined using an income approach. Actual cash flows are likely to be different than those assumed.

3.    Collaborative Arrangements

Merck has entered into collaborative arrangements that provide the Company with varying rights to develop, produce and market products together with its collaborative partners. Both parties in these arrangements are active participants and exposed to significant risks and rewards dependent on the commercial success of the activities of the collaboration. Merck’s more significant collaborative arrangements are discussed below.

AstraZeneca

In July 2017, Merck and AstraZeneca PLC (AstraZeneca) entered into a global strategic oncology collaboration to co-develop and co-commercialize AstraZeneca’s Lynparza (olaparib) for multiple cancer types. Lynparza is an oral poly (ADP-ribose) polymerase (PARP) inhibitor currently approved for certain types of advanced ovarian, breast, pancreatic and prostate cancers. The companies are jointly developing and commercializing Lynparza, both as monotherapy and in combination trials with other potential medicines. Independently, Merck and AstraZeneca will develop and commercialize Lynparza in combinations with their respective PD-1 and PD-L1 medicines, Keytruda and Imfinzi. The companies will also jointly develop and commercialize AstraZeneca’s Koselugo (selumetinib), an oral, selective inhibitor of MEK, part of the mitogen-activated protein kinase (MAPK) pathway, currently being developed for multiple indications. In April 2020, Koselugo was approved by the U.S. Food and Drug Administration (FDA) for the treatment of pediatric patients two years of age and older with neurofibromatosis type 1 who have symptomatic, inoperable plexiform neurofibromas. Under the terms of the agreement, AstraZeneca and Merck will share the development and commercialization costs for Lynparza and Koselugo monotherapy and non-PD-L1/PD-1 combination therapy opportunities.

Profits from Lynparza and Koselugo product sales generated through monotherapies or combination therapies are shared equally. Merck will fund all development and commercialization costs of Keytruda in combination with Lynparza or Koselugo. AstraZeneca will fund all development and commercialization costs of Imfinzi in combination with Lynparza or Koselugo. AstraZeneca is the principal on Lynparza and Koselugo sales transactions. Merck records its share of Lynparza and Koselugo product sales, net of cost of sales and commercialization costs, as alliance revenue and its share of development costs associated with the collaboration as part of Research and development expenses. Reimbursements received from AstraZeneca for research and development expenses are recognized as reductions to Research and development costs.

As part of the agreement, Merck made an upfront payment to AstraZeneca of $1.6 billion in 2017 and made payments of $750 million over a multi-year period for certain license options. In addition, the agreement provides for additional contingent payments from Merck to AstraZeneca related to the successful achievement of sales-based and regulatory milestones.

In the second quarter of 2020, Merck determined it was probable that sales of Lynparza in the future would trigger $400 million of sales-based milestone payments from Merck to AstraZeneca. Accordingly, Merck recorded a $400 million liability and a corresponding increase to the intangible asset related to Lynparza. Prior to 2020, Merck accrued sales-based milestone payments aggregating $1.0 billion related to Lynparza, of which $200 million and $250 million was paid to AstraZeneca in 2019 and 2018, respectively, and $250 million was paid in the first nine months of 2020. Potential future sales-based milestone payments of $2.7 billion have not yet been accrued as they are not deemed by the Company to be probable at this time.

In the second quarter of 2020, Lynparza received regulatory approvals triggering capitalized milestone payments of $135 million from Merck to AstraZeneca. In 2019 and 2018, Lynparza received regulatory approvals triggering capitalized milestone payments of $60 million and $140 million, respectively, in the aggregate from Merck to AstraZeneca. Potential future regulatory milestone payments of $1.4 billion remain under the agreement.

The intangible asset balance related to Lynparza (which includes capitalized sales-based and regulatory milestone payments) was $1.3 billion at September 30, 2020 and is included in Other Intangibles, Net on the Consolidated Balance Sheet. The amount is being amortized over its estimated useful life through 2028 as supported by projected future cash flows, subject to impairment testing.

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Notes to Condensed Consolidated Financial Statements (unaudited) (continued)

Summarized financial information related to this collaboration is as follows:

			Three Months Ended September 30,												Nine Months Ended September 30,
($ in millions)			2020						2019						2020						2019
Alliance revenue - Lynparza			$	196					$	123					$	519					$	313
Alliance revenue - Koselugo			3						—						3						—
Total alliance revenue			$	199					$	123					$	522					$	313
Cost of sales (1)			41						28						205						120
Selling, general and administrative			40						36						112						96
Research and development			20						44						93						122
($ in millions)															September 30, 2020						December 31, 2019
Receivables from AstraZeneca included in Other current assets															$	197					$	128
Payables to AstraZeneca included in Accrued and other current liabilities (2)															309						577
Payables to AstraZeneca included in Other Noncurrent Liabilities (2)															400						—

(1) Represents amortization of capitalized milestone payments.

(2) Includes accrued milestone payments.

Eisai

In March 2018, Merck and Eisai Co., Ltd. (Eisai) announced a strategic collaboration for the worldwide co-development and co-commercialization of Lenvima (lenvatinib), an orally available tyrosine kinase inhibitor discovered by Eisai. Lenvima is currently approved for the treatment of certain types of thyroid cancer, hepatocellular carcinoma, in combination with everolimus for certain patients with renal cell carcinoma, and in combination with Keytruda for the treatment of certain patients with endometrial carcinoma. Under the agreement, Merck and Eisai will develop and commercialize Lenvima jointly, both as monotherapy and in combination with Keytruda. Eisai records Lenvima product sales globally (Eisai is the principal on Lenvima sales transactions), and Merck and Eisai share profits equally. Merck records its share of Lenvima product sales, net of cost of sales and commercialization costs, as alliance revenue. Expenses incurred during co-development, including for studies evaluating Lenvima as monotherapy, are shared equally by the two companies and reflected in Research and development expenses.

Under the agreement, Merck made an upfront payment to Eisai of $750 million and agreed to make payments of up to $650 million for certain option rights through 2021 (of which $325 million was paid in March 2019, $200 million was paid in March 2020 and $125 million is expected to be paid in March 2021). In addition, the agreement provides for additional contingent payments from Merck to Eisai related to the successful achievement of sales-based and regulatory milestones.

In the second quarter of 2020, Merck determined it was probable that sales of Lenvima in the future would trigger sales-based milestone payments aggregating $370 million from Merck to Eisai. Accordingly, Merck recorded a $370 million liability and a corresponding increase to the intangible asset related to Lenvima. Prior to 2020, Merck accrued sales-based milestone payments aggregating $950 million. Of these amounts, $50 million was paid to Eisai in 2019 and an additional $500 million was paid in the first nine months of 2020. Potential future sales-based milestone payments of $2.7 billion have not yet been accrued as they are not deemed by the Company to be probable at this time.

In 2018, Lenvima received regulatory approvals triggering capitalized milestone payments of $250 million in the aggregate from Merck to Eisai. Potential future regulatory milestone payments of $135 million remain under the agreement.

The intangible asset balance related to Lenvima (which includes capitalized sales-based and regulatory milestone payments) was $1.1 billion at September 30, 2020 and is included in Other Intangibles, Net on the Consolidated Balance Sheet. The amount is being amortized over its estimated useful life through 2026 as supported by projected future cash flows, subject to impairment testing.

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Notes to Condensed Consolidated Financial Statements (unaudited) (continued)

Summarized financial information related to this collaboration is as follows:

			Three Months Ended September 30,												Nine Months Ended September 30,
($ in millions)			2020						2019						2020						2019
Alliance revenue - Lenvima			$	142					$	109					$	421					$	280
Cost of sales (1)			46						23						215						97
Selling, general and administrative			18						21						48						59
Research and development			48						37						168						146
($ in millions)															September 30, 2020						December 31, 2019
Receivables from Eisai included in Other current assets															$	170					$	150
Payables to Eisai included in Accrued and other current liabilities (2)															325						700
Payables to Eisai included in Other Noncurrent Liabilities (3)															570						525

(1) Represents amortization of capitalized milestone payments.

(2) Includes accrued milestone and future option payments.

(3) Includes accrued milestone payments.

Bayer AG

In 2014, the Company entered into a worldwide clinical development collaboration with Bayer AG (Bayer) to market and develop soluble guanylate cyclase (sGC) modulators including Bayer’s Adempas (riociguat), which is approved to treat pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension. The two companies have implemented a joint development and commercialization strategy. The collaboration also includes clinical development of Bayer’s vericiguat, which is in development for the potential treatment of worsening heart failure. Vericiguat is currently under review by regulatory authorities in the United States, the EU and Japan. Under the agreement, Bayer leads commercialization of Adempas in the Americas, while Merck leads commercialization in the rest of the world. For vericiguat, if approved, Bayer will lead commercialization in the rest of world and Merck will lead in the Americas. Both companies share in development costs and profits on sales and have the right to co-promote in territories where they are not the lead. Merck records sales of Adempas in its marketing territories, as well as alliance revenue, which is Merck’s share of profits from the sale of Adempas in Bayer’s marketing territories. In addition, the agreement provides for contingent payments from Merck to Bayer related to the successful achievement of sales-based milestones.

Prior to 2020, Merck accrued $725 million of sales-based milestone payments for this collaboration, of which $350 million was paid to Bayer in 2018. There is an additional $400 million potential future sales-based milestone payment that has not yet been accrued as it is not deemed by the Company to be probable at this time.

The intangible asset balance related to this collaboration (which includes the acquired intangible asset balance, as well as capitalized sales-based milestone payments) was $838 million at September 30, 2020 and is included in Other Intangibles, Net on the Consolidated Balance Sheet. The amount is being amortized over its estimated useful life through 2027 as supported by projected future cash flows, subject to impairment testing.

Summarized financial information related to this collaboration is as follows:

			Three Months Ended September 30,												Nine Months Ended September 30,
($ in millions)			2020						2019						2020						2019
Alliance revenue - Adempas			$	83					$	50					$	216					$	144
Net sales of Adempas recorded by Merck			55						57						167						158
Total sales			$	138					$	107					$	383					$	302
Cost of sales (1)			29						28						85						86
Selling, general and administrative			19						12						42						31
Research and development			12						31						53						94
($ in millions)															September 30, 2020						December 31, 2019
Receivables from Bayer included in Other current assets															$	70					$	49
Payables to Bayer included in Other Noncurrent Liabilities (2)															375						375

(1) Includes amortization of intangible assets.

(2) Represents accrued milestone payment.

- 12 -

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Notes to Condensed Consolidated Financial Statements (unaudited) (continued)

4.    Restructuring

In early 2019, Merck approved a new global restructuring program (Restructuring Program) as part of a worldwide initiative focused on further optimizing the Company’s manufacturing and supply network, as well as reducing its global real estate footprint. This program is a continuation of the Company’s plant rationalization, builds on prior restructuring programs and does not include any actions associated with the planned spin-off of Organon. As the Company continues to evaluate its global footprint and overall operating model, it subsequently identified additional actions under the Restructuring Program, and could identify further actions over time. The actions currently contemplated under the Restructuring Program are expected to be substantially completed by the end of 2023, with the cumulative pretax costs to be incurred by the Company to implement the program estimated to be approximately $2.5 billion. The Company estimates that approximately 60% of the cumulative pretax costs will result in cash outlays, primarily related to employee separation expense and facility shut-down costs. Approximately 40% of the cumulative pretax costs will be non-cash, relating primarily to the accelerated depreciation of facilities to be closed or divested. The Company expects to record charges of approximately $800 million in 2020 related to the Restructuring Program. Actions under previous global restructuring programs have been substantially completed.

The Company recorded total pretax costs of $186 million and $296 million in the third quarter of 2020 and 2019, respectively, and $504 million and $642 million for the first nine months of 2020 and 2019, respectively, related to restructuring program activities. Since inception of the Restructuring Program through September 30, 2020, Merck has recorded total pretax accumulated costs of approximately $1.4 billion. For segment reporting, restructuring charges are unallocated expenses.

The following tables summarize the charges related to restructuring program activities by type of cost:

			Three Months Ended September 30, 2020																								Nine Months Ended September 30, 2020
($ in millions)			Separation Costs						Accelerated Depreciation						Other						Total						Separation Costs						Accelerated Depreciation						Other						Total
Cost of sales			$	—					$	33					$	5					$	38					$	—					$	89					$	42					$	131
Selling, general and administrative			—						15						—						15						—						37						—						37
Research and development			—						18						1						19						—						66						1						67
Restructuring costs			61						—						53						114						143						—						126						269
			$	61					$	66					$	59					$	186					$	143					$	192					$	169					$	504

			Three Months Ended September 30, 2019																								Nine Months Ended September 30, 2019
($ in millions)			Separation Costs						Accelerated Depreciation						Other						Total						Separation Costs						Accelerated Depreciation						Other						Total
Cost of sales			$	—					$	41					$	21					$	62					$	—					$	139					$	22					$	161
Selling, general and administrative			—						1						—						1						—						33						—						33
Research and development			—						(1)						2						1						—						1						3						4
Restructuring costs			205						—						27						232						358						—						86						444
			$	205					$	41					$	50					$	296					$	358					$	173					$	111					$	642

Separation costs are associated with actual headcount reductions, as well as those headcount reductions which were probable and could be reasonably estimated.

Accelerated depreciation costs primarily relate to manufacturing, research and administrative facilities and equipment to be sold or closed as part of the programs. Accelerated depreciation costs represent the difference between the depreciation expense to be recognized over the revised useful life of the asset, based upon the anticipated date the site will be closed or divested or the equipment disposed of, and depreciation expense as determined utilizing the useful life prior to the restructuring actions. All the sites have and will continue to operate up through the respective closure dates and, since future undiscounted cash flows are sufficient to recover the respective book values, Merck is recording accelerated depreciation over the revised useful life of the site assets. Anticipated site closure dates, particularly related to manufacturing locations, have been and may continue to be adjusted to reflect changes resulting from regulatory or other factors.

Other activity in 2020 and 2019 includes asset abandonment, facility shut-down and other related costs, as well as pretax gains and losses resulting from the sales of facilities and related assets. Additionally, other activity includes certain employee-related costs associated with pension and other postretirement benefit plans (see Note 12) and share-based compensation.

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Notes to Condensed Consolidated Financial Statements (unaudited) (continued)

The following table summarizes the charges and spending relating to restructuring program activities for the nine months ended September 30, 2020:

($ in millions)			Separation Costs						Accelerated Depreciation						Other						Total
Restructuring reserves January 1, 2020			$	690					$	—					$	69					$	759
Expense			143						192						169						504
(Payments) receipts, net			(395)						—						(237)						(632)
Non-cash activity			—						(192)						39						(153)
Restructuring reserves September 30, 2020 (1)			$	438					$	—					$	40					$	478

(1)The remaining cash outlays are expected to be substantially completed by the end of 2023.

5.    Financial Instruments

Derivative Instruments and Hedging Activities

The Company manages the impact of foreign exchange rate movements and interest rate movements on its earnings, cash flows and fair values of assets and liabilities through operational means and through the use of various financial instruments, including derivative instruments.

A significant portion of the Company’s revenues and earnings in foreign affiliates is exposed to changes in foreign exchange rates. The objectives and accounting related to the Company’s foreign currency risk management program, as well as its interest rate risk management activities are discussed below.

Foreign Currency Risk Management

The Company has established revenue hedging, balance sheet risk management and net investment hedging programs to protect against volatility of future foreign currency cash flows and changes in fair value caused by changes in foreign exchange rates.

The objective of the revenue hedging program is to reduce the variability caused by changes in foreign exchange rates that would affect the U.S. dollar value of future cash flows derived from foreign currency denominated sales, primarily the euro, Japanese yen and Chinese renminbi. To achieve this objective, the Company will hedge a portion of its forecasted foreign currency denominated third-party and intercompany distributor entity sales (forecasted sales) that are expected to occur over its planning cycle, typically no more than two years into the future. The Company will layer in hedges over time, increasing the portion of forecasted sales hedged as it gets closer to the expected date of the forecasted sales. The portion of forecasted sales hedged is based on assessments of cost-benefit profiles that consider natural offsetting exposures, revenue and exchange rate volatilities and correlations, and the cost of hedging instruments. The Company manages its anticipated transaction exposure principally with purchased local currency put options, forward contracts and purchased collar options.

The fair values of these derivative contracts are recorded as either assets (gain positions) or liabilities (loss positions) in the Condensed Consolidated Balance Sheet. Changes in the fair value of derivative contracts are recorded each period in either current earnings or Other comprehensive income (OCI), depending on whether the derivative is designated as part of a hedge transaction and, if so, the type of hedge transaction. For derivatives that are designated as cash flow hedges, the unrealized gains or losses on these contracts are recorded in Accumulated other comprehensive income (AOCI) and reclassified into Sales when the hedged anticipated revenue is recognized. For those derivatives which are not designated as cash flow hedges, but serve as economic hedges of forecasted sales, unrealized gains or losses are recorded in Sales each period. The cash flows from both designated and non-designated contracts are reported as operating activities in the Condensed Consolidated Statement of Cash Flows. The Company does not enter into derivatives for trading or speculative purposes.

The Company manages operating activities and net asset positions at each local subsidiary in order to mitigate the effects of exchange on monetary assets and liabilities. The Company also uses a balance sheet risk management program to mitigate the exposure of net monetary assets that are denominated in a currency other than a subsidiary’s functional currency from the effects of volatility in foreign exchange. In these instances, Merck principally utilizes forward exchange contracts to offset the effects of exchange on exposures denominated in developed country currencies, primarily the euro and Japanese yen. For exposures in developing country currencies, the Company will enter into forward contracts to partially offset the effects of exchange on exposures when it is deemed economical to do so based on a cost-benefit analysis that considers the magnitude of the exposure, the volatility of the exchange rate and the cost of the hedging instrument. The cash flows from these contracts are reported as operating activities in the Condensed Consolidated Statement of Cash Flows.

Monetary assets and liabilities denominated in a currency other than the functional currency of a given subsidiary are remeasured at spot rates in effect on the balance sheet date with the effects of changes in spot rates reported in Other (income) expense, net. The forward contracts are not designated as hedges and are marked to market through Other (income) expense, net. Accordingly, fair value changes in the forward contracts help mitigate the changes in the value of the remeasured

- 14 -

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Notes to Condensed Consolidated Financial Statements (unaudited) (continued)

assets and liabilities attributable to changes in foreign currency exchange rates, except to the extent of the spot-forward differences. These differences are not significant due to the short-term nature of the contracts, which typically have average maturities at inception of less than one year.

The Company also uses forward exchange contracts to hedge a portion of its net investment in foreign operations against movements in exchange rates. The forward contracts are designated as hedges of the net investment in a foreign operation. The unrealized gains or losses on these contracts are recorded in foreign currency translation adjustment within OCI and remain in AOCI until either the sale or complete or substantially complete liquidation of the subsidiary. The Company excludes certain portions of the change in fair value of its derivative instruments from the assessment of hedge effectiveness (excluded components). Changes in fair value of the excluded components are recognized in OCI. The Company recognizes in earnings the initial value of the excluded components on a straight-line basis over the life of the derivative instrument, rather than using the mark-to-market approach. The cash flows from these contracts are reported as investing activities in the Condensed Consolidated Statement of Cash Flows.

Foreign exchange risk is also managed through the use of foreign currency debt. The Company’s senior unsecured euro-denominated notes have been designated as, and are effective as, economic hedges of the net investment in a foreign operation. Accordingly, foreign currency transaction gains or losses due to spot rate fluctuations on the euro-denominated debt instruments are included in foreign currency translation adjustment within OCI.

The effects of the Company’s net investment hedges on OCI and the Consolidated Statement of Income are shown below:

			Amount of Pretax (Gain) Loss Recognized in Other Comprehensive Income (1)																								Amount of Pretax (Gain) Loss Recognized in Other (income) expense, net for Amounts Excluded from Effectiveness Testing
			Three Months Ended September 30,												Nine Months Ended September 30,												Three Months Ended September 30,												Nine Months Ended September 30,
($ in millions)			2020						2019						2020						2019						2020						2019						2020						2019
Net Investment Hedging Relationships
Foreign exchange contracts			$	10					$	1					$	15					$	8					$	(4)					$	(8)					$	(15)					$	(23)
Euro-denominated notes			162						(150)						182						(152)						—						—						—						—

(1) No amounts were reclassified from AOCI into income related to the sale of a subsidiary.

Interest Rate Risk Management

The Company may use interest rate swap contracts on certain investing and borrowing transactions to manage its net exposure to interest rate changes and to reduce its overall cost of borrowing. The Company does not use leveraged swaps and, in general, does not leverage any of its investment activities that would put principal capital at risk.

In February 2020, five interest rate swaps with notional amounts of $250 million each matured. These swaps effectively converted the Company’s $1.25 billion, 1.85% fixed-rate notes due 2020 to variable rate debt. At September 30, 2020, the Company was a party to 14 pay-floating, receive-fixed interest rate swap contracts designated as fair value hedges of fixed-rate notes in which the notional amounts match the amount of the hedged fixed-rate notes as detailed in the table below.

			September 30, 2020
($ in millions)			Par Value of Debt						Number of Interest Rate Swaps Held						Total Swap Notional Amount
3.875% notes due 2021			$	1,150					5						$	1,150
2.40% notes due 2022			1,000						4						1,000
2.35% notes due 2022			1,250						5						1,250

The interest rate swap contracts are designated hedges of the fair value changes in the notes attributable to changes in the benchmark London Interbank Offered Rate (LIBOR) swap rate. The fair value changes in the notes attributable to changes in the LIBOR swap rate are recorded in interest expense along with the offsetting fair value changes in the swap contracts. The cash flows from these contracts are reported as operating activities in the Condensed Consolidated Statement of Cash Flows.

- 15 -

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Notes to Condensed Consolidated Financial Statements (unaudited) (continued)

The table below presents the location of amounts recorded on the Consolidated Balance Sheet related to cumulative basis adjustments for fair value hedges:

			Carrying Amount of Hedged Liabilities												Cumulative Amount of Fair Value Hedging Adjustment Increase (Decrease) Included in the Carrying Amount
($ in millions)			September 30, 2020						December 31, 2019						September 30, 2020						December 31, 2019
Balance Sheet Line Item in which Hedged Item is Included
Loans payable and current portion of long-term debt			$	1,155					$	1,249					$	5					$	(1)
Long-Term Debt			2,309						3,409						62						14

Presented in the table below is the fair value of derivatives on a gross basis segregated between those derivatives that are designated as hedging instruments and those that are not designated as hedging instruments:

						September 30, 2020																		December 31, 2019
						Fair Value of Derivative												U.S. Dollar Notional						Fair Value of Derivative												U.S. Dollar Notional
($ in millions)			Balance Sheet Caption			Asset						Liability												Asset						Liability
Derivatives Designated as Hedging Instruments
Interest rate swap contracts			Other current assets			$	6					$	—					$	1,150					$	—					$	—					$	—
Interest rate swap contracts			Other Assets			63						—						2,250						15						—						3,400
Interest rate swap contracts			Accrued and other current liabilities			—						—						—						—						1						1,250
Foreign exchange contracts			Other current assets			30						—						4,120						152						—						6,117
Foreign exchange contracts			Other Assets			59						—						1,881						55						—						2,160
Foreign exchange contracts			Accrued and other current liabilities			—						104						3,096						—						22						1,748
Foreign exchange contracts			Other Noncurrent Liabilities			—						1						157						—						1						53
						$	158					$	105					$	12,654					$	222					$	24					$	14,728
Derivatives Not Designated as Hedging Instruments
Foreign exchange contracts			Other current assets			$	81					$	—					$	5,455					$	66					$	—					$	7,245
Foreign exchange contracts			Accrued and other current liabilities			—						171						8,042						—						73						8,693
Forward contract related to Seagen common stock			Accrued and other current liabilities			—						22						1,000						—						—						—
						$	81					$	193					$	14,497					$	66					$	73					$	15,938
						$	239					$	298					$	27,151					$	288					$	97					$	30,666

As noted above, the Company records its derivatives on a gross basis in the Condensed Consolidated Balance Sheet. The Company has master netting agreements with several of its financial institution counterparties (see Concentrations of Credit Risk below). The following table provides information on the Company’s derivative positions subject to these master netting arrangements as if they were presented on a net basis, allowing for the right of offset by counterparty and cash collateral exchanged per the master agreements and related credit support annexes:

			September 30, 2020												December 31, 2019
($ in millions)			Asset						Liability						Asset						Liability
Gross amounts recognized in the condensed consolidated balance sheet			$	239					$	298					$	288					$	97
Gross amounts subject to offset in master netting arrangements not offset in the condensed consolidated balance sheet			(140)						(140)						(84)						(84)
Cash collateral received			—						—						(34)						—
Net amounts			$	99					$	158					$	170					$	13

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Notes to Condensed Consolidated Financial Statements (unaudited) (continued)

The table below provides information regarding the location and amount of pretax (gains) losses of derivatives designated in fair value or cash flow hedging relationships:

			Sales												Other (income) expense, net (1)												Other comprehensive income (loss)												Sales												Other (income) expense, net (1)												Other comprehensive income (loss)
			Three Months Ended September 30,												Three Months Ended September 30,												Three Months Ended September 30,												Nine Months Ended September 30,												Nine Months Ended September 30,												Nine Months Ended September 30,
($ in millions)			2020						2019						2020						2019						2020						2019						2020						2019						2020						2019						2020						2019
Financial Statement Line Items in which Effects of Fair Value or Cash Flow Hedges are Recorded			$	12,551					$	12,397					$	(312)					$	35					$	10					$	(28)					$	35,479					$	34,972					$	(630)					$	362					$	(190)					$	155
(Gain) loss on fair value hedging relationships
Interest rate swap contracts
Hedged items			—						—						(14)						13						—						—						—						—						54						101						—						—
Derivatives designated as hedging instruments			—						—						—						(6)						—						—						—						—						(76)						(74)						—						—
Impact of cash flow hedging relationships
Foreign exchange contracts
Amount of (loss) gain recognized in OCI on derivatives			—						—						—						—						(195)						186						—						—						—						—						(126)						183
Increase (decrease) in Sales as a result of AOCI reclassifications			(23)						70						—						—						23						(70)						65						189						—						—						(65)						(189)
Interest rate contracts
Amount of gain recognized in Other (income) expense, net on derivatives			—						—						(1)						(1)						—						—						—						—						(3)						(3)						—						—
Amount of loss recognized in OCI on derivatives			—						—						—						—						(1)						(1)						—						—						—						—						(3)						(6)

(1) Interest expense is a component of Other (income) expense, net.

The table below provides information regarding the income statement effects of derivatives not designated as hedging instruments:

									Amount of Derivative Pretax (Gain) Loss Recognized in Income
									Three Months Ended September 30,												Nine Months Ended September 30,
($ in millions)			Income Statement Caption						2020						2019						2020						2019
Derivatives Not Designated as Hedging Instruments
Foreign exchange contracts (1)			Other (income) expense, net						$	(7)					$	(8)					$	(138)					$	112
Foreign exchange contracts (2)			Sales						7						(11)						4						(7)
Interest rate contracts (3)			Other (income) expense, net						—						—						9						—
Forward contract related to Seagen common stock			Research and development expenses						22						—						22						—

(1) These derivative contracts mitigate changes in the value of remeasured foreign currency denominated monetary assets and liabilities attributable to changes in foreign currency exchange rates.

(2) These derivative contracts serve as economic hedges of forecasted transactions.

(3) These derivatives serve as economic hedges against rising treasury rates.

At September 30, 2020, the Company estimates $155 million of pretax net unrealized losses on derivatives maturing within the next 12 months that hedge foreign currency denominated sales over that same period will be reclassified from AOCI to Sales. The amount ultimately reclassified to Sales may differ as foreign exchange rates change. Realized gains and losses are ultimately determined by actual exchange rates at maturity.

- 17 -

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Notes to Condensed Consolidated Financial Statements (unaudited) (continued)

Investments in Debt and Equity Securities

Information on investments in debt and equity securities is as follows:

			September 30, 2020																								December 31, 2019
			Amortized Cost						Gross Unrealized												Fair Value						Amortized Cost						Gross Unrealized												Fair Value
($ in millions)									Gains						Losses																		Gains						Losses
U.S. government and agency securities			$	74					$	—					$	—					$	74					$	266					$	3					$	—					$	269
Foreign government bonds			2						—						—						2						—						—						—						—
Commercial paper			—						—						—						—						668						—						—						668
Corporate notes and bonds			—						—						—						—						608						13						—						621
Asset-backed securities			—						—						—						—						226						1						—						227
Total debt securities			$	76					$	—					$	—					$	76					$	1,768					$	17					$	—					$	1,785
Publicly traded equity securities (1)																					1,477																								838
Total debt and publicly traded equity securities																					$	1,553																							$	2,623

(1) Unrealized net (gains) losses recognized in Other (income) expense, net on equity securities still held at September 30, 2020 were $(43) million and $(512) million in the third quarter and first nine months of 2020, respectively. Unrealized net losses (gains) recognized in Other (income) expense, net on equity securities still held at September 30, 2019 were $25 million and $(41) million in the third quarter and first nine months of 2019, respectively.

At September 30, 2020 and September 30, 2019, the Company also had $508 million and $393 million, respectively, of equity investments without readily determinable fair values included in Other Assets. The Company recognizes unrealized gains on these equity investments based on favorable observable price changes from transactions involving similar investments of the same investee and recognizes unrealized losses based on unfavorable observable price changes. During the first nine months of 2020, the Company recognized unrealized gains of $21 million and unrealized losses of $3 million in Other (income) expense, net related to these equity investments held at September 30, 2020. During the first nine months of 2019, the Company recognized unrealized gains of $4 million and unrealized losses of $12 million in Other (income) expense, net related to these investments held at September 30, 2019. Cumulative unrealized gains and cumulative unrealized losses based on observable prices changes for investments in equity investments without readily determinable fair values still held at September 30, 2020 were $128 million and $24 million, respectively.

Fair Value Measurements

Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The Company uses a fair value hierarchy which maximizes the use of observable inputs and minimizes the use of unobservable inputs when measuring fair value. There are three levels of inputs used to measure fair value with Level 1 having the highest priority and Level 3 having the lowest: Level 1 - Quoted prices (unadjusted) in active markets for identical assets or liabilities; Level 2 - Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities; Level 3 - Unobservable inputs that are supported by little or no market activity. Level 3 assets or liabilities are those whose values are determined using pricing models, discounted cash flow methodologies, or similar techniques with significant unobservable inputs, as well as assets or liabilities for which the determination of fair value requires significant judgment or estimation. If the inputs used to measure the financial assets and liabilities fall within more than one level described above, the categorization is based on the lowest level input that is significant to the fair value measurement of the instrument.

- 18 -

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Notes to Condensed Consolidated Financial Statements (unaudited) (continued)

Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis

Financial assets and liabilities measured at fair value on a recurring basis are summarized below:

			Fair Value Measurements Using																								Fair Value Measurements Using
			Level 1						Level 2						Level 3						Total						Level 1						Level 2						Level 3						Total
($ in millions)			September 30, 2020																								December 31, 2019
Assets
Investments
Foreign government bonds			$	—					$	2					$	—					$	2					$	—					$	—					$	—					$	—
Commercial paper			—						—						—						—						—						668						—						668
Corporate notes and bonds			—						—						—						—						—						621						—						621
Asset-backed securities (1)			—						—						—						—						—						227						—						227
U.S. government and agency securities			—						—						—						—						—						209						—						209
Publicly traded equity securities			1,370						—						—						1,370						518						—						—						518
			1,370						2						—						1,372						518						1,725						—						2,243
Other assets (2)
U.S. government and agency securities			74						—						—						74						60						—						—						60
Publicly traded equity securities			107						—						—						107						320						—						—						320
			181						—						—						181						380						—						—						380
Derivative assets (3)
Forward exchange contracts			—						116						—						116						—						169						—						169
Interest rate swaps			—						69						—						69						—						15						—						15
Purchased currency options			—						54						—						54						—						104						—						104
			—						239						—						239						—						288						—						288
Total assets			$	1,551					$	241					$	—					$	1,792					$	898					$	2,013					$	—					$	2,911
Liabilities
Other liabilities
Contingent consideration			$	—					$	—					$	829					$	829					$	—					$	—					$	767					$	767
Derivative liabilities (3)
Forward exchange contracts			—						275						—						275						—						95						—						95
Forward contract related to Seagen common stock			—						22						—						22						—						—						—						—
Written currency options			—						1						—						1						—						1						—						1
Interest rate swaps			—						—						—						—						—						1						—						1
			—						298						—						298						—						97						—						97
Total liabilities			$	—					$	298					$	829					$	1,127					$	—					$	97					$	767					$	864

(1)Primarily all of the asset-backed securities were highly rated (Standard & Poor’s rating of AAA and Moody’s Investors Service rating of Aaa), secured primarily by auto loan, credit card and student loan receivables, with weighted-average lives of primarily 5 years or less.

(2)    Investments included in other assets are restricted as to use, including for the payment of benefits under employee benefit plans.

(3)    The fair value determination of derivatives includes the impact of the credit risk of counterparties to the derivatives and the Company’s own credit risk, the effects of which were not significant.

As of September 30, 2020 and December 31, 2019, Cash and cash equivalents included $6.6 billion and $8.9 billion of cash equivalents, respectively (which would be considered Level 2 in the fair value hierarchy).

- 19 -

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Notes to Condensed Consolidated Financial Statements (unaudited) (continued)

Contingent Consideration

Summarized information about the changes in liabilities for contingent consideration associated with business acquisitions is as follows:

			Nine Months Ended September 30,
($ in millions)			2020						2019
Fair value January 1			$	767					$	788
Additions			97						—
Changes in estimated fair value (1)			71						52
Payments			(106)						(85)
Fair value September 30 (2)(3)			$	829					$	755

(1) Recorded in Cost of sales, Research and development expenses, and Other (income) expense, net. Includes cumulative translation adjustments.

(2) Balance at September 30, 2020 includes $140 million recorded as a current liability for amounts expected to be paid within the next 12 months.

(3) At September 30, 2020 and December 31, 2019, $637 million and $625 million, respectively, of the liabilities relate to the termination of the Sanofi-Pasteur MSD joint venture in 2016. As part of the termination, Merck recorded a liability for contingent future royalty payments of 11.5% on net sales of all Merck products that were previously sold by the joint venture through December 31, 2024. The fair value of this liability is determined utilizing the estimated amount and timing of projected cash flows using a risk-adjusted discount rate of 8% to present value the cash flows.

The additions to contingent consideration in 2020 relate to the acquisition of Themis (see Note 2). The payments of contingent consideration in both periods relate to liabilities recorded in connection with the termination of the Sanofi-Pasteur MSD joint venture in 2016.

Other Fair Value Measurements

Some of the Company’s financial instruments, such as cash and cash equivalents, receivables and payables, are reflected in the balance sheet at carrying value, which approximates fair value due to their short-term nature.

The estimated fair value of loans payable and long-term debt (including current portion) at September 30, 2020, was $32.6 billion compared with a carrying value of $28.7 billion and at December 31, 2019, was $28.8 billion compared with a carrying value of $26.3 billion. Fair value was estimated using recent observable market prices and would be considered Level 2 in the fair value hierarchy.

Concentrations of Credit Risk

On an ongoing basis, the Company monitors concentrations of credit risk associated with corporate and government issuers of securities and financial institutions with which it conducts business. Credit exposure limits are established to limit a concentration with any single issuer or institution. Cash and investments are placed in instruments that meet high credit quality standards as specified in the Company’s investment policy guidelines.

The majority of the Company’s accounts receivable arise from product sales in the United States, Europe and China and are primarily due from drug wholesalers and retailers, hospitals, government agencies, managed health care providers and pharmacy benefit managers. The Company monitors the financial performance and creditworthiness of its customers so that it can properly assess and respond to changes in their credit profile. The Company also continues to monitor global economic conditions, including the volatility associated with international sovereign economies, and associated impacts on the financial markets and its business.

The Company has accounts receivable factoring agreements with financial institutions in certain countries to sell accounts receivable. The Company factored $2.1 billion and $2.7 billion of accounts receivable in the third quarter of 2020 and the fourth quarter of 2019, respectively, under these factoring arrangements, which reduced outstanding accounts receivable. The cash received from the financial institutions is reported within operating activities in the Consolidated Statement of Cash Flows. In certain of these factoring arrangements, for ease of administration, the Company will collect customer payments related to the factored receivables, which it then remits to the financial institutions. The net cash flows relating to these collections are reported as financing activities in the Consolidated Statement of Cash Flows. The cost of factoring such accounts receivable was de minimis.

Derivative financial instruments are executed under International Swaps and Derivatives Association master agreements. The master agreements with several of the Company’s financial institution counterparties also include credit support annexes. These annexes contain provisions that require collateral to be exchanged depending on the value of the derivative assets and liabilities, the Company’s credit rating, and the credit rating of the counterparty. Cash collateral received by the Company from various counterparties was $34 million at December 31, 2019. The obligation to return such collateral is recorded in Accrued and other current liabilities. No cash collateral was advanced by the Company to counterparties as of September 30, 2020 or December 31, 2019.

- 20 -

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Notes to Condensed Consolidated Financial Statements (unaudited) (continued)

6.    Inventories

Inventories consisted of:

($ in millions)			September 30, 2020						December 31, 2019
Finished goods			$	2,038					$	1,772
Raw materials and work in process			6,073						5,650
Supplies			197						207
Total (approximates current cost)			8,308						7,629
Decrease to LIFO cost			(99)						(171)
			$	8,209					$	7,458
Recognized as:
Inventories			$	6,128					$	5,978
Other assets			2,081						1,480

Amounts recognized as Other Assets are comprised almost entirely of raw materials and work in process inventories. At September 30, 2020 and December 31, 2019, these amounts included $1.8 billion and $1.3 billion, respectively, of inventories not expected to be sold within one year. In addition, these amounts included $288 million and $168 million at September 30, 2020 and December 31, 2019, respectively, of inventories produced in preparation for product launches.

7.    Other Intangibles

During the third quarter and first nine months of 2019, the Company recorded $612 million and $693 million, respectively, of intangible asset impairment charges related to marketed products within Cost of sales. During the third quarter of 2019, the Company recorded an impairment charge of $612 million related to Sivextro (tedizolid phosphate), a product for the treatment of acute bacterial skin and skin structure infections caused by susceptible isolates of certain Gram-positive microorganisms. As part of a reorganization and reprioritization of its internal sales force, the Company made the decision to cease promotion of Sivextro in the U.S. market by the end of 2019. This decision resulted in reduced cash flow projections for Sivextro, which indicated that the Sivextro intangible asset value was not fully recoverable on an undiscounted cash flows basis. The Company utilized market participant assumptions to determine its best estimate of the fair value of the intangible asset related to Sivextro that, when compared with its related carrying value, resulted in the impairment charge noted above.

8.    Long-Term Debt

In June 2020, the Company issued $4.5 billion principal amount of senior unsecured notes consisting of $1.0 billion of 0.75% notes due 2026, $1.25 billion of 1.45% notes due 2030, $1.0 billion of 2.35% notes due 2040 and $1.25 billion of 2.45% notes due 2050. Merck used the net proceeds from the offering for general corporate purposes, including without limitation the repayment of outstanding commercial paper borrowings and other indebtedness with upcoming maturities.

9.    Contingencies

The Company is involved in various claims and legal proceedings of a nature considered normal to its business, including product liability, intellectual property, and commercial litigation, as well as certain additional matters including governmental and environmental matters. In the opinion of the Company, it is unlikely that the resolution of these matters will be material to the Company’s financial condition, results of operations or cash flows.

Given the nature of the litigation discussed below and the complexities involved in these matters, the Company is unable to reasonably estimate a possible loss or range of possible loss for such matters until the Company knows, among other factors, (i) what claims, if any, will survive dispositive motion practice, (ii) the extent of the claims, including the size of any potential class, particularly when damages are not specified or are indeterminate, (iii) how the discovery process will affect the litigation, (iv) the settlement posture of the other parties to the litigation and (v) any other factors that may have a material effect on the litigation.

The Company records accruals for contingencies when it is probable that a liability has been incurred and the amount can be reasonably estimated. These accruals are adjusted periodically as assessments change or additional information becomes available. For product liability claims, a portion of the overall accrual is actuarially determined and considers such factors as past experience, number of claims reported and estimates of claims incurred but not yet reported. Individually significant contingent losses are accrued when probable and reasonably estimable. Legal defense costs expected to be incurred in connection with a loss contingency are accrued when probable and reasonably estimable.

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Notes to Condensed Consolidated Financial Statements (unaudited) (continued)

The Company’s decision to obtain insurance coverage is dependent on market conditions, including cost and availability, existing at the time such decisions are made. The Company has evaluated its risks and has determined that the cost of obtaining product liability insurance outweighs the likely benefits of the coverage that is available and, as such, has no insurance for most product liabilities.

Product Liability Litigation

Fosamax

As previously disclosed, Merck is a defendant in product liability lawsuits in the United States involving Fosamax (Fosamax Litigation). As of September 30, 2020, approximately 3,590 cases are pending against Merck in either federal or state court. Plaintiffs in the vast majority of these cases generally allege that they sustained femur fractures and/or other bone injuries (Femur Fractures) in association with the use of Fosamax.

All federal cases involving allegations of Femur Fractures have been or will be transferred to a multidistrict litigation in the District of New Jersey (Femur Fracture MDL). In the only bellwether case tried to date in the Femur Fracture MDL, Glynn v. Merck, the jury returned a verdict in Merck’s favor. In addition, in June 2013, the Femur Fracture MDL court granted Merck’s motion for judgment as a matter of law in the Glynn case and held that the plaintiff’s failure to warn claim was preempted by federal law.

In August 2013, the Femur Fracture MDL court entered an order requiring plaintiffs in the Femur Fracture MDL to show cause why those cases asserting claims for a femur fracture injury that took place prior to September 14, 2010, should not be dismissed based on the court’s preemption decision in the Glynn case. Pursuant to the show cause order, in March 2014, the Femur Fracture MDL court dismissed with prejudice approximately 650 cases on preemption grounds. Plaintiffs in approximately 515 of those cases appealed that decision to the U.S. Court of Appeals for the Third Circuit (Third Circuit). In March 2017, the Third Circuit issued a decision reversing the Femur Fracture MDL court’s preemption ruling and remanding the appealed cases back to the Femur Fracture MDL court. In May 2019, the U.S. Supreme Court decided that the Third Circuit had incorrectly concluded that the issue of preemption should be resolved by a jury, and accordingly vacated the judgment of the Third Circuit and remanded the proceedings back to the Third Circuit to address the issue in a manner consistent with the Supreme Court’s opinion. In November 2019, the Third Circuit remanded the cases back to the District Court in order to allow that court to determine in the first instance whether the plaintiffs’ state law claims are preempted by federal law under the standards described by the Supreme Court in its opinion. Briefing on the issue is closed, and the parties await the decision of the District Court.

Accordingly, as of September 30, 2020, approximately 970 cases were actively pending in the Femur Fracture MDL.

As of September 30, 2020, approximately 2,340 cases alleging Femur Fractures have been filed in New Jersey state court and are pending before Judge James Hyland in Middlesex County. The parties selected an initial group of cases to be reviewed through fact discovery, and Merck has continued to select additional cases to be reviewed.

As of September 30, 2020, approximately 275 cases alleging Femur Fractures have been filed and are pending in California state court. All of the Femur Fracture cases filed in California state court have been coordinated before a single judge in Orange County, California.

Additionally, there are four Femur Fracture cases pending in other state courts.

Discovery is presently stayed in the Femur Fracture MDL and in the state court in California. Merck intends to defend against these lawsuits.

Januvia/Janumet

As previously disclosed, Merck is a defendant in product liability lawsuits in the United States involving Januvia and/or Janumet. As of September 30, 2020, Merck is aware of approximately 1,465 product users alleging that Januvia and/or Janumet caused the development of pancreatic cancer and other injuries.

Most claims have been filed in multidistrict litigation before the U.S. District Court for the Southern District of California (MDL). Outside of the MDL, the majority of claims have been filed in coordinated proceedings before the Superior Court of California, County of Los Angeles (California State Court).

In November 2015, the MDL and California State Court–in separate opinions–granted summary judgment to defendants on grounds of federal preemption.

Plaintiffs appealed in both forums. In November 2017, the U.S. Court of Appeals for the Ninth Circuit vacated the judgment and remanded for further discovery. In November 2018, the California state appellate court reversed and remanded on similar grounds. In March 2019, the parties in the MDL and the California coordinated proceedings agreed to coordinate and adopt a schedule for completing discovery on general causation and preemption issues and for renewing summary judgment

- 22 -

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Notes to Condensed Consolidated Financial Statements (unaudited) (continued)

and Daubert motions. Under the stipulated case management schedule, the hearings for Daubert and summary judgment motions took place on October 20, 2020.

As of September 30, 2020, six product users have claims pending against Merck in state courts other than California, including Illinois. In June 2017, the Illinois trial court denied Merck’s motion for summary judgment based on federal preemption. Merck appealed, and the Illinois appellate court affirmed in December 2018. Merck filed a petition for leave to appeal to the Illinois Supreme Court in February 2019. In April 2019, the Illinois Supreme Court stayed consideration of the pending petition to appeal until the U.S. Supreme Court issued its opinion in Merck Sharp & Dohme Corp. v. Albrecht (relating to the Fosamax matter discussed above). Merck filed the opinion in Albrecht with the Illinois Supreme Court in June 2019. The petition for leave to appeal was decided in September 2019, in which the Illinois Supreme Court directed the intermediate appellate court to reconsider its earlier ruling. The Illinois Appellate Court issued a favorable decision concluding, consistent with Albrecht, that preemption presents a legal question to be resolved by the court.

In addition to the claims noted above, the Company has agreed to toll the statute of limitations for approximately 50 additional claims. The Company intends to continue defending against these lawsuits.

Vioxx

As previously disclosed, Merck is a defendant in a lawsuit brought by the Attorney General of Utah alleging that Merck misrepresented the safety of Vioxx. The lawsuit is pending in Utah state court. Utah seeks damages and penalties under the Utah False Claims Act. A bench trial in this matter has been rescheduled for April 6, 2021.

Governmental Proceedings

As previously disclosed, the Company’s subsidiaries in China have received and may continue to receive inquiries regarding their operations from various Chinese governmental agencies. Some of these inquiries may be related to matters involving other multinational pharmaceutical companies, as well as Chinese entities doing business with such companies. The Company’s policy is to cooperate with these authorities and to provide responses as appropriate.

As previously disclosed, from time to time, the Company receives inquiries and is the subject of preliminary investigation activities from competition and other governmental authorities in markets outside the United States. These authorities may include regulators, administrative authorities, and law enforcement and other similar officials, and these preliminary investigation activities may include site visits, formal or informal requests or demands for documents or materials, inquiries or interviews and similar matters. Certain of these preliminary inquiries or activities may lead to the commencement of formal proceedings. Should those proceedings be determined adversely to the Company, monetary fines and/or remedial undertakings may be required.

Commercial and Other Litigation

Zetia Antitrust Litigation

As previously disclosed, Merck, MSD, Schering Corporation and MSP Singapore Company LLC (collectively, the Merck Defendants) are defendants in putative class action and opt-out lawsuits filed in 2018 on behalf of direct and indirect purchasers of Zetia alleging violations of federal and state antitrust laws, as well as other state statutory and common law causes of action. The cases have been consolidated for pretrial purposes in a federal multidistrict litigation before Judge Rebecca Beach Smith in the Eastern District of Virginia. In December 2018, the court denied the Merck Defendants’ motions to dismiss or stay the direct purchaser putative class actions pending bilateral arbitration. In August 2019, the district court adopted in full the report and recommendation of the magistrate judge with respect to the Merck Defendants’ motions to dismiss on non-arbitration issues, thereby granting in part and denying in part Merck Defendants’ motions to dismiss. In addition, in June 2019, the representatives of the putative direct purchaser class filed an amended complaint, and in August 2019, retailer opt-out plaintiffs filed an amended complaint. The Merck Defendants moved to dismiss the new allegations in both complaints. In October 2019, the magistrate judge issued a report and recommendation recommending that the district judge grant the motions in their entirety. In December 2019, the district court adopted this report and recommendation in part. The district court granted the Merck Defendants’ motion to dismiss to the extent the motion sought dismissal of claims for overcharges paid by entities that purchased generic ezetimibe from Par Pharmaceutical, Inc. (Par Pharmaceutical) and dismissed any claims for such overcharges. In November 2019, the direct purchaser plaintiffs and the indirect purchaser plaintiffs filed motions for class certification. On June 18, 2020, the magistrate judge issued a report and recommendation recommending that the district judge grant in part the direct purchasers’ motion for class certification and certify a class of 35 direct purchasers. On August 21, 2020, the district court adopted the report and recommendation in full, and on November 2, 2020, the U.S. Court of Appeals for the Fourth Circuit granted defendants’ motion for permission to appeal the district court’s order. Also, on August 14, 2020, the magistrate judge recommended that the court grant the motion for class certification filed by the putative indirect purchaser class. The Merck Defendants objected to this report and recommendation and are awaiting a decision from the district court.

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Notes to Condensed Consolidated Financial Statements (unaudited) (continued)

On August 10, 2020, the Merck Defendants filed a motion for summary judgment and other motions, and plaintiffs filed a motion for partial summary judgment, and other motions. Those motions are now fully briefed, and the court will likely hold a hearing on the competing motions. Trial in this matter has been adjourned.

Patent Litigation

From time to time, generic manufacturers of pharmaceutical products file abbreviated New Drug Applications (NDAs) with the FDA seeking to market generic forms of the Company’s products prior to the expiration of relevant patents owned by the Company. To protect its patent rights, the Company may file patent infringement lawsuits against such generic companies. Similar lawsuits defending the Company’s patent rights may exist in other countries. The Company intends to vigorously defend its patents, which it believes are valid, against infringement by companies attempting to market products prior to the expiration of such patents. As with any litigation, there can be no assurance of the outcomes, which, if adverse, could result in significantly shortened periods of exclusivity for these products and, with respect to products acquired through acquisitions, potentially significant intangible asset impairment charges.

Bridion — Between January and March 2020, the Company received multiple Paragraph IV Certification Letters under the Hatch-Waxman Act notifying the Company that generic drug companies have filed applications to the FDA seeking pre-patent expiry approval to sell generic versions of Bridion (sugammadex) Injection. In March and April 2020, the Company filed patent infringement lawsuits in the U.S. District Courts for the District of New Jersey and the Northern District of West Virginia against those generic companies. These lawsuits, which assert one or more patents covering sugammadex and methods of using sugammadex, automatically stay FDA approval of the generic applications until June 2023 or until adverse court decisions, if any, whichever may occur earlier.

Mylan Pharmaceuticals Inc., Mylan API US LLC, and Mylan Inc. (Mylan) have filed motions to dismiss in the District of New Jersey for lack of venue and failure to state a claim against certain defendants, and in the Northern District of West Virginia for failure to state a claim against certain defendants. The New Jersey motion has not yet been decided, and the West Virginia action is stayed pending resolution of the New Jersey motion. All New Jersey actions against all defendants have been consolidated.

Januvia, Janumet, Janumet XR — In February 2019, Par Pharmaceutical filed suit against the Company in the U.S. District Court for the District of New Jersey, seeking a declaratory judgment of invalidity of a patent owned by the Company covering certain salt and polymorphic forms of sitagliptin that expires in 2026. In response, the Company filed a patent infringement lawsuit in the U.S. District Court for the District of Delaware against Par Pharmaceutical and additional companies that also indicated an intent to market generic versions of Januvia, Janumet, and Janumet XR following expiration of key patent protection in 2022, but prior to the expiration of the later-granted patent owned by the Company covering certain salt and polymorphic forms of sitagliptin that expires in 2026 (2026 salt/polymorph patent), and a later granted patent owned by the Company covering the Janumet formulation which expires in 2028. Par Pharmaceutical dismissed its case in the U.S. District Court for the District of New Jersey against the Company and will litigate the action in the U.S. District Court for the District of Delaware. The Company filed a patent infringement lawsuit against Mylan in the Northern District of West Virginia. The Judicial Panel of Multidistrict Litigation entered an order transferring the Company’s lawsuit against Mylan to the U.S. District Court for the District of Delaware for coordinated and consolidated pretrial proceedings with the other cases pending in that district. The U.S. District Court for the District of Delaware has scheduled the lawsuits for a single three-day trial on invalidity issues in October 2021. The Court will schedule separate one-day trials on infringement issues if necessary. In the Company’s case against Mylan, the U.S. District Court for the Northern District of West Virginia has conditionally scheduled a three-day trial in December 2021 on all issues. In February 2020, the Company amended its complaint against one defendant, Teva Pharmaceuticals USA, Inc., to add patent infringement claims related to a patent that expires in 2025 and covers certain processes for manufacturing sitagliptin. In July 2020, the Company amended its complaints against two defendants, Teva Pharmaceuticals USA, Inc. and Watson Laboratories, Inc., to add patent infringement claims related to a patent that also expires in 2026 and covers certain amorphous forms of sitagliptin.

The Company has settled with five generic companies such that these generic companies can bring their products to the market in November 2026 or earlier under certain circumstances.

In October 2019, Mylan filed a petition for Inter Partes Review (IPR) at the United States Patent and Trademark Office (USPTO) seeking invalidity of some, but not all, of the claims of the 2026 salt/polymorph patent. The USPTO instituted IPR proceedings in May 2020, finding a reasonable likelihood that the challenged claims are not valid. A trial is scheduled for February 2021 and a final decision is expected in May 2021. After institution, three additional IPR petitions were filed by Teva Pharmaceuticals USA, Inc., Dr. Reddy’s Laboratories, Inc., and Sun Pharmaceutical Industries Ltd., as well as related entities, which requested joinder with Mylan’s IPR proceedings. If the challenges are successful, the unchallenged claims of the 2026 salt/polymorph patent will remain valid, subject to the court proceedings described above.

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Notes to Condensed Consolidated Financial Statements (unaudited) (continued)

In Germany, two generic companies have sought the revocation of the Supplementary Protection Certificate (SPC) for Janumet. If the generic companies are successful, Janumet could lose market exclusivity in Germany as early as July 2022. Challenges to the Janumet SPC have also occurred in Portugal and Finland, and could occur in other European countries.

Other Litigation

There are various other pending legal proceedings involving the Company, principally product liability and intellectual property lawsuits. While it is not feasible to predict the outcome of such proceedings, in the opinion of the Company, either the likelihood of loss is remote or any reasonably possible loss associated with the resolution of such proceedings is not expected to be material to the Company’s financial condition, results of operations or cash flows either individually or in the aggregate.

Legal Defense Reserves

Legal defense costs expected to be incurred in connection with a loss contingency are accrued when probable and reasonably estimable. Some of the significant factors considered in the review of these legal defense reserves are as follows: the actual costs incurred by the Company; the development of the Company’s legal defense strategy and structure in light of the scope of its litigation; the number of cases being brought against the Company; the costs and outcomes of completed trials and the most current information regarding anticipated timing, progression, and related costs of pre-trial activities and trials in the associated litigation. The amount of legal defense reserves as of September 30, 2020 and December 31, 2019 of approximately $255 million and $240 million, respectively, represents the Company’s best estimate of the minimum amount of defense costs to be incurred in connection with its outstanding litigation; however, events such as additional trials and other events that could arise in the course of its litigation could affect the ultimate amount of legal defense costs to be incurred by the Company. The Company will continue to monitor its legal defense costs and review the adequacy of the associated reserves and may determine to increase the reserves at any time in the future if, based upon the factors set forth, it believes it would be appropriate to do so.

10.    Equity

			Three Months Ended September 30,
			Common Stock						Other Paid-In Capital			Retained Earnings			Accumulated Other Comprehensive Loss			Treasury Stock						Non- controlling Interests			Total
($ and shares in millions except per share amounts)			Shares			Par Value												Shares			Cost
Balance at July 1, 2019			3,577			$	1,788		$	39,484		$	45,295		$	(5,362)		1,010			$	(53,570)		$	102		$	27,737
Net income attributable to Merck & Co., Inc.			—			—			—			1,901			—			—			—			—			1,901
Other comprehensive loss, net of taxes			—			—			—			—			(28)			—			—			—			(28)
Cash dividends declared on common stock ($0.55 per share)			—			—			—			(1,392)			—			—			—			—			(1,392)
Treasury stock shares purchased			—			—			—			—			—			17			(1,405)			—			(1,405)
Share-based compensation plans and other			—			—			77			—			—			(1)			50			—			127
Net income attributable to noncontrolling interests			—			—			—			—			—			—			—			6			6
Distributions attributable to noncontrolling interests			—			—			—			—			—			—			—			(21)			(21)
Balance at September 30, 2019			3,577			$	1,788		$	39,561		$	45,804		$	(5,390)		1,026			$	(54,925)		$	87		$	26,925
Balance at July 1, 2020			3,577			$	1,788		$	39,373		$	49,724		$	(6,393)		1,048			$	(56,850)		$	102		$	27,744
Net income attributable to Merck & Co., Inc.			—			—			—			2,941			—			—			—			—			2,941
Other comprehensive income, net of taxes			—			—			—			—			10			—			—			—			10
Cash dividends declared on common stock ($0.61 per share)			—			—			—			(1,558)			—			—			—			—			(1,558)
Share-based compensation plans and other			—			—			116			—			—			(1)			35			—			151
Net income attributable to noncontrolling interests			—			—			—			—			—			—			—			4			4
Distributions attributable to noncontrolling interests			—			—			—			—			—			—			—			(22)			(22)
Balance at September 30, 2020			3,577			$	1,788		$	39,489		$	51,107		$	(6,383)		1,047			$	(56,815)		$	84		$	29,270

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Notes to Condensed Consolidated Financial Statements (unaudited) (continued)

			Nine Months Ended September 30,
			Common Stock						Other Paid-In Capital			Retained Earnings			Accumulated Other Comprehensive Loss			Treasury Stock						Non- controlling Interests			Total
($ and shares in millions except per share amounts)			Shares			Par Value												Shares			Cost
Balance at January 1, 2019			3,577			$	1,788		$	38,808		$	42,579		$	(5,545)		985			$	(50,929)		$	181		$	26,882
Net income attributable to Merck & Co., Inc.			—			—			—			7,487			—			—			—			—			7,487
Other comprehensive income, net of taxes			—			—			—			—			155			—			—			—			155
Cash dividends declared on common stock ($1.65 per share)			—			—			—			(4,262)			—			—			—			—			(4,262)
Treasury stock shares purchased			—			—			1,000			—			—			54			(4,730)			—			(3,730)
Share-based compensation plans and other			—			—			(247)			—			—			(13)			734			—			487
Net loss attributable to noncontrolling interests			—			—			—			—			—			—			—			(73)			(73)
Distributions attributable to noncontrolling  interests			—			—			—			—			—			—			—			(21)			(21)
Balance at September 30, 2019			3,577			1,788			39,561			45,804			(5,390)			1,026			(54,925)			87			26,925
Balance at January 1, 2020			3,577			$	1,788		$	39,660		$	46,602		$	(6,193)		1,038			$	(55,950)		$	94		$	26,001
Net income attributable to Merck & Co., Inc.			—			—			—			9,161			—			—			—			—			9,161
Other comprehensive loss, net of taxes			—			—			—			—			(190)			—			—			—			(190)
Cash dividends declared on common stock ($1.83 per share)			—			—			—			(4,656)			—			—			—			—			(4,656)
Treasury stock shares purchased			—			—			—			—			—			16			(1,281)			—			(1,281)
Share-based compensation plans and other			—			—			(171)			—			—			(7)			416			—			245
Net income attributable to noncontrolling interests			—			—			—			—			—			—			—			12			12
Distributions attributable to noncontrolling  interests			—			—			—			—			—			—			—			(22)			(22)
Balance at September 30, 2020			3,577			$	1,788		$	39,489		$	51,107		$	(6,383)		1,047			$	(56,815)		$	84		$	29,270

11.    Share-Based Compensation Plans

The Company has share-based compensation plans under which the Company grants restricted stock units (RSUs) and performance share units (PSUs) to certain management level employees. In addition, employees and non-employee directors may be granted options to purchase shares of Company common stock at the fair market value at the time of grant.

The following table provides the amounts of share-based compensation cost recorded in the Condensed Consolidated Statement of Income:

			Three Months Ended September 30,												Nine Months Ended September 30,
($ in millions)			2020						2019						2020						2019
Pretax share-based compensation expense			$	126					$	101					$	354					$	306
Income tax benefit			(17)						(14)						(48)						(42)
Total share-based compensation expense, net of taxes			$	109					$	87					$	306					$	264

During the first nine months of 2020, the Company granted 7 million RSUs with a weighted-average grant date fair value of $77.83 per RSU and during the first nine months of 2019 granted 5 million RSUs with a weighted-average grant date fair value of $80.03 per RSU. During the first nine months of 2020, the Company granted 773 thousand PSUs with a weighted-average grant date fair value of $75.22 per PSU and during the first nine months of 2019 granted 609 thousand PSUs with a weighted-average grant date fair value of $90.50 per PSU.

During the first nine months of 2020, the Company granted 4 million stock options with a weighted-average exercise price of $77.67 per option and during the first nine months of 2019 granted 3 million stock options with a weighted-average exercise price of $80.05 per option. The weighted-average fair value of options granted during the first nine months of 2020 and 2019 was $9.93 and $10.63 per option, respectively, and was determined using the following assumptions:

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Notes to Condensed Consolidated Financial Statements (unaudited) (continued)

			Nine Months Ended September 30,
			2020						2019
Expected dividend yield			3.1		%				3.2		%
Risk-free interest rate			0.4		%				2.4		%
Expected volatility			22.1		%				18.7		%
Expected life (years)			5.8						5.9

At September 30, 2020, there was $800 million of total pretax unrecognized compensation expense related to nonvested stock options, RSU and PSU awards which will be recognized over a weighted-average period of 2.1 years. For segment reporting, share-based compensation costs are unallocated expenses.

12.    Pension and Other Postretirement Benefit Plans

The Company has defined benefit pension plans covering eligible employees in the United States and in certain of its international subsidiaries. The net periodic benefit cost of such plans consisted of the following components: 

			Three Months Ended September 30,																								Nine Months Ended September 30,
			2020												2019												2020												2019
($ in millions)			U.S.						International						U.S.						International						U.S.						International						U.S.						International
Service cost			$	96					$	77					$	76					$	58					$	270					$	225					$	221					$	178
Interest cost			107						35						115						44						323						103						343						133
Expected return on plan assets			(193)						(104)						(202)						(106)						(581)						(310)						(613)						(320)
Amortization of unrecognized prior service credit			(12)						(3)						(12)						(3)						(37)						(9)						(37)						(9)
Net loss amortization			75						32						43						16						228						94						113						47
Termination benefits			1						1						3						—						5						2						7						1
Curtailments			1						—						5						—						4						(1)						6						—
Settlements			2						—						—						—						11						2						—						—
			$	77					$	38					$	28					$	9					$	223					$	106					$	40					$	30

The Company anticipates that in 2020 it will contribute approximately $200 million and $375 million to its U.S. and international pension plans, respectively, of which $184 million and $123 million, respectively, was contributed in the first nine months of the year.

The Company provides medical benefits, principally to its eligible U.S. retirees and similar benefits to their dependents, through its other postretirement benefit plans. The net credit of such plans consisted of the following components: 

			Three Months Ended September 30,												Nine Months Ended September 30,
($ in millions)			2020						2019						2020						2019
Service cost			$	13					$	12					$	39					$	36
Interest cost			14						17						43						52
Expected return on plan assets			(19)						(18)						(56)						(54)
Amortization of unrecognized prior service credit			(18)						(20)						(54)						(59)
Net gain amortization			(5)						(3)						(13)						(7)
Termination benefits			—						1						—						1
Curtailments			—						(3)						(1)						(4)
			$	(15)					$	(14)					$	(42)					$	(35)

In connection with restructuring actions (see Note 4), termination charges were recorded on pension plans related to expanded eligibility for certain employees exiting Merck. Also, in connection with these restructuring actions, curtailments were recorded on pension and other postretirement benefit plans and settlements were recorded on certain U.S. and international pension plans as reflected in the tables above.

The components of net periodic benefit cost (credit) other than the service cost component are included in Other (income) expense, net (see Note 13), with the exception of certain amounts for termination benefits, curtailments and

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Notes to Condensed Consolidated Financial Statements (unaudited) (continued)

settlements, which are recorded in Restructuring costs if the event giving rise to the termination benefits, curtailment or settlement is related to restructuring actions as noted above.

13.    Other (Income) Expense, Net

Other (income) expense, net, consisted of: 

			Three Months Ended September 30,												Nine Months Ended September 30,
($ in millions)			2020						2019						2020						2019
Interest income			$	(9)					$	(61)					$	(48)					$	(225)
Interest expense			203						231						624						674
Exchange losses			10						38						89						166
Income from investments in equity securities, net (1)			(360)						(16)						(964)						(50)
Net periodic defined benefit plan (credit) cost other than service cost			(88)						(128)						(259)						(409)
Other, net			(68)						(29)						(72)						206
			$	(312)					$	35					$	(630)					$	362

(1)    Includes net realized and unrealized gains and losses from investments in equity securities either owned directly or through ownership interests in investment funds. Unrealized gains and losses from investments that are directly owned are determined at the end of the reporting period, while ownership interests in investment funds are accounted for on a one quarter lag.

The decline in interest income in the third quarter and first nine months of 2020 reflects lower investments and lower interest rates. The lower exchange losses in the first nine months of 2020 reflect losses on forward exchange contracts in 2019 related to the acquisition of Antelliq. The increase in income from investments in equity securities, net, in both the third quarter and first nine months of 2020 was driven primarily by the recognition of unrealized gains on certain investments, most of which relate to Moderna, Inc.

Other, net (as reflected in the table above) in the first nine months of 2019 includes $162 million of goodwill impairment charges related to certain businesses in the Healthcare Services segment.

Interest paid for the nine months ended September 30, 2020 and 2019 was $605 million and $629 million, respectively.

14.    Taxes on Income

The effective income tax rates of 14.1% and 18.7% for the third quarter of 2020 and 2019, respectively, and 14.9% and 14.5% for the first nine months of 2020 and 2019, respectively, reflect the impacts of acquisition and divestiture-related costs and restructuring costs, partially offset by the beneficial impact of foreign earnings. The effective income tax rates in the third quarter and first nine months of 2019 also reflect the unfavorable impact of a charge for the acquisition of Peloton for which no tax benefit was recognized and the favorable impact of product mix on the estimated 2019 full-year tax rate. In addition, the effective income tax rate for the first nine months of 2019 reflects the favorable impact of a $360 million net tax benefit related to the settlement of certain federal income tax matters.

In the first quarter of 2019, the Internal Revenue Service (IRS) concluded its examinations of Merck’s 2012-2014 U.S. federal income tax returns. As a result, the Company was required to make a payment of $107 million. The Company’s reserves for unrecognized tax benefits for the years under examination exceeded the adjustments relating to this examination period and therefore the Company recorded a $360 million net tax benefit in the first nine months of 2019. This net benefit reflects reductions in reserves for unrecognized tax benefits for tax positions relating to the years that were under examination, partially offset by additional reserves for tax positions not previously reserved for.

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Notes to Condensed Consolidated Financial Statements (unaudited) (continued)

15.    Earnings Per Share

The calculations of earnings per share are as follows:

			Three Months Ended September 30,												Nine Months Ended September 30,
($ and shares in millions except per share amounts)			2020						2019						2020						2019
Net income attributable to Merck & Co., Inc.			$	2,941					$	1,901					$	9,161					$	7,487
Average common shares outstanding			2,529						2,558						2,530						2,572
Common shares issuable (1)			9						14						11						15
Average common shares outstanding assuming dilution			2,538						2,572						2,541						2,587
Basic earnings per common share attributable to Merck & Co., Inc. common shareholders			$	1.16					$	0.74					$	3.62					$	2.91
Earnings per common share assuming dilution attributable to Merck & Co., Inc. common shareholders			$	1.16					$	0.74					$	3.61					$	2.89

(1)Issuable primarily under share-based compensation plans.

For the third quarter of 2020 and 2019, 5 million and 3 million, respectively, and for the first nine months of 2020 and 2019, 5 million and 2 million, respectively, of common shares issuable under share-based compensation plans were excluded from the computation of earnings per common share assuming dilution because the effect would have been antidilutive.

16.    Other Comprehensive Income (Loss)

Changes in AOCI by component are as follows:

			Three Months Ended September 30,
($ in millions)			Derivatives						Investments						Employee Benefit Plans						Cumulative Translation Adjustment						Accumulated Other Comprehensive Income (Loss)
Balance July 1, 2019, net of taxes			$	66					$	48					$	(3,530)					$	(1,946)					$	(5,362)
Other comprehensive income (loss) before reclassification adjustments, pretax			186						8						(4)						(84)						106
Tax			(39)						—						—						(33)						(72)
Other comprehensive income (loss) before reclassification adjustments, net of taxes			147						8						(4)						(117)						34
Reclassification adjustments, pretax			(71)			(1)			(25)			(2)			21			(3)			—						(75)
Tax			15						—						(2)						—						13
Reclassification adjustments, net of taxes			(56)						(25)						19						—						(62)
Other comprehensive income (loss), net of taxes			91						(17)						15						(117)						(28)
Balance September 30, 2019, net of taxes			$	157					$	31					$	(3,515)					$	(2,063)					$	(5,390)
Balance July 1, 2020, net of taxes			$	15					$	—					$	(4,162)					$	(2,246)					$	(6,393)
Other comprehensive income (loss) before reclassification adjustments, pretax			(195)						—						2						50						(143)
Tax			41						—						1						35						77
Other comprehensive income (loss) before reclassification adjustments, net of taxes			(154)						—						3						85						(66)
Reclassification adjustments, pretax			22			(1)			—						72			(3)			—						94
Tax			(5)						—						(13)						—						(18)
Reclassification adjustments, net of taxes			17						—						59						—						76
Other comprehensive income (loss), net of taxes			(137)						—						62						85						10
Balance September 30, 2020, net of taxes			$	(122)					$	—					$	(4,100)					$	(2,161)					$	(6,383)

- 29 -

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Notes to Condensed Consolidated Financial Statements (unaudited) (continued)

			Nine Months Ended September 30,
($ in millions)			Derivatives						Investments						Employee Benefit Plans						Cumulative Translation Adjustment						Accumulated Other Comprehensive Income (Loss)
Balance January 1, 2019, net of taxes			$	166					$	(78)					$	(3,556)					$	(2,077)					$	(5,545)
Other comprehensive income (loss) before reclassification adjustments, pretax			183						139						(5)						47						364
Tax			(38)						—						6						(33)						(65)
Other comprehensive income (loss) before reclassification adjustments, net of taxes			145						139						1						14						299
Reclassification adjustments, pretax			(195)			(1)			(30)			(2)			49			(3)			—						(176)
Tax			41						—						(9)						—						32
Reclassification adjustments, net of taxes			(154)						(30)						40						—						(144)
Other comprehensive income (loss), net of taxes			(9)						109						41						14						155
Balance September 30, 2019, net of taxes			$	157					$	31					$	(3,515)					$	(2,063)					$	(5,390)
Balance January 1, 2020, net of taxes			$	31					$	18					$	(4,261)					$	(1,981)					$	(6,193)
Other comprehensive income (loss) before reclassification adjustments, pretax			(126)						3						(19)						(220)						(362)
Tax			27						—						12						40						79
Other comprehensive income (loss) before reclassification adjustments, net of taxes			(99)						3						(7)						(180)						(283)
Reclassification adjustments, pretax			(68)			(1)			(21)			(2)			210			(3)			—						121
Tax			14						—						(42)						—						(28)
Reclassification adjustments, net of taxes			(54)						(21)						168						—						93
Other comprehensive income (loss), net of taxes			(153)						(18)						161						(180)						(190)
Balance September 30, 2020, net of taxes			$	(122)					$	—					$	(4,100)					$	(2,161)					$	(6,383)

(1) Relates to foreign currency cash flow hedges that were reclassified from AOCI to Sales.

(2) Represents net realized (gains) losses on the sales of available-for-sale debt securities that were reclassified from AOCI to Other (income) expense, net.

(3) Includes net amortization of prior service cost and actuarial gains and losses included in net periodic benefit cost (see Note 12).

17.    Segment Reporting

The Company’s operations are principally managed on a products basis and include three operating segments, which are the Pharmaceutical, Animal Health and Healthcare Services segments. The Pharmaceutical and Animal Health segments are the only reportable segments.

The Pharmaceutical segment includes human health pharmaceutical and vaccine products. Human health pharmaceutical products consist of therapeutic and preventive agents, generally sold by prescription, for the treatment of human disorders. The Company sells these human health pharmaceutical products primarily to drug wholesalers and retailers, hospitals, government agencies and managed health care providers such as health maintenance organizations, pharmacy benefit managers and other institutions. Human health vaccine products consist of preventive pediatric, adolescent and adult vaccines, primarily administered at physician offices. The Company sells these human health vaccines primarily to physicians, wholesalers, physician distributors and government entities. A large component of pediatric and adolescent vaccine sales are made to the U.S. Centers for Disease Control and Prevention Vaccines for Children program, which is funded by the U.S. government. Additionally, the Company sells vaccines to the Federal government for placement into vaccine stockpiles.

The Animal Health segment discovers, develops, manufactures and markets a wide range of veterinary pharmaceutical and vaccine products, as well as health management solutions and services, for the prevention, treatment and control of disease in all major livestock and companion animal species. The Company also offers an extensive suite of digitally connected identification, traceability and monitoring products. The Company sells its products to veterinarians, distributors and animal producers.

The Healthcare Services segment provided services and solutions that focus on engagement, health analytics and clinical services to improve the value of care delivered to patients. The Company has been in the process of divesting the businesses in the Healthcare Services segment. The remaining businesses were divested during the first quarter of 2020.

- 30 -

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Notes to Condensed Consolidated Financial Statements (unaudited) (continued)

Sales of the Company’s products were as follows:

			Three Months Ended September 30,																																				Nine Months Ended September 30,
			2020																		2019																		2020																		2019
($ in millions)			U.S.						Int’l						Total						U.S.						Int’l						Total						U.S.						Int’l						Total						U.S.						Int’l						Total
Pharmaceutical:
Oncology
Keytruda			$	2,157					$	1,559					$	3,715					$	1,743					$	1,327					$	3,070					$	6,106					$	4,281					$	10,387					$	4,525					$	3,448					$	7,973
Alliance revenue - Lynparza (1)			107						89						196						71						53						123						297						223						519						186						126						313
Alliance revenue - Lenvima (1)			82						60						142						65						44						109						270						152						421						169						112						280
Emend			8						31						39						42						56						98						18						96						115						173						163						336
Vaccines
Gardasil/Gardasil 9			579						608						1,187						761						558						1,320						1,209						1,732						2,941						1,579						1,464						3,044
ProQuad/M-M-R II/Varivax			437						139						576						482						141						623						1,033						356						1,390						1,325						469						1,794
Pneumovax 23			276						99						375						179						58						237						478						270						748						428						164						592
RotaTeq			114						96						210						102						78						180						355						246						601						360						203						564
Vaqta			32						19						51						36						26						62						79						60						139						103						65						167
Hospital Acute Care
Bridion			162						157						320						133						151						284						412						431						843						381						437						817
Noxafil			13						66						79						77						100						177						27						220						247						268						291						560
Prevymis			32						46						77						22						23						45						87						113						200						60						55						115
Primaxin			1						73						74						2						75						77						2						187						189						2						204						207
Invanz			1						50						51						(1)						58						57						7						152						159						30						176						206
Cancidas			1						49						50						—						62						62						2						147						148						5						187						191
Cubicin			11						28						39						14						38						52						36						80						116						78						129						207
Zerbaxa			20						23						43						20						15						35						57						54						112						45						43						88
Immunology
Simponi			—						209						209						—						203						203						—						615						615						—						625						625
Remicade			—						82						82						—						101						101						—						242						242						—						322						322
Neuroscience
Belsomra			18						63						81						23						57						80						67						177						244						68						155						223
Virology
Isentress/Isentress HD			92						113						205						102						149						250						243						403						646						304						449						752
Zepatier			6						22						28						24						59						83						38						83						122						96						208						304
Cardiovascular
Zetia			(1)						103						103						5						142						147						(4)						389						384						11						432						443
Vytorin			3						44						47						5						52						57						9						130						139						11						219						231
Atozet			—						111						111						—						97						97						—						348						348						—						283						283
Alliance revenue - Adempas (2)			78						5						83						48						2						50						200						16						216						137						7						144
Adempas			—						55						55						—						57						57						—						167						167						—						158						158
Diabetes
Januvia			342						479						821						367						440						807						1,110						1,339						2,449						1,223						1,317						2,539
Janumet			105						400						506						129						375						503						361						1,138						1,499						462						1,105						1,567
Women’s Health
Implanon/Nexplanon			137						52						189						136						62						199						374						142						515						421						160						581
NuvaRing			24						34						58						202						39						241						85						98						184						593						107						700
Diversified Brands
Singulair			4						78						82						11						140						152						14						324						338						24						479						503
Cozaar/Hyzaar			5						86						91						6						110						116						17						275						292						16						313						329
Arcoxia			—						68						68						—						72						72						—						204						204						—						221						221
Nasonex			—						41						41						4						55						58						9						152						161						2						224						226
Follistim AQ			20						31						50						27						35						62						60						76						136						80						102						182
Other pharmaceutical (3)			352						834						1,186						343						804						1,149						1,144						2,334						3,478						1,037						2,394						3,431
Total Pharmaceutical segment sales			5,218						6,102						11,320						5,180						5,914						11,095						14,202						17,452						31,654						14,202						17,016						31,218
Animal Health:
Livestock			164						594						758						144						582						726						448						1,697						2,145						406						1,601						2,007
Companion Animals			234						228						462						193						203						396						676						714						1,390						560						704						1,264
Total Animal Health segment sales			398						822						1,220						337						785						1,122						1,124						2,411						3,535						966						2,305						3,271
Other segment sales (4)			—						—						—						46						—						46						23						—						23						133						1						133
Total segment sales			5,616						6,924						12,540						5,563						6,699						12,263						15,349						19,863						35,212						15,301						19,322						34,622
Other (5)			9						2						11						10						125						134						47						221						267						19						330						350
			$	5,625					$	6,926					$	12,551					$	5,573					$	6,824					$	12,397					$	15,396					$	20,084					$	35,479					$	15,320					$	19,652					$	34,972

U.S. plus international may not equal total due to rounding.

(1)    Alliance revenue represents Merck’s share of profits, which are product sales net of cost of sales and commercialization costs (see Note 3).

(2)    Alliance revenue represents Merck’s share of profits from sales in Bayer’s marketing territories, which are product sales net of cost of sales and commercialization costs (see Note 3).

(3)    Other pharmaceutical primarily reflects sales of other human health pharmaceutical products, including products within the franchises not listed separately.

(4)    Represents sales for the Healthcare Services segment. All the businesses in the Healthcare Services segment were divested as of March 31, 2020.

(5)    Other is primarily comprised of miscellaneous corporate revenues, including revenue hedging activities, as well as third-party manufacturing sales.

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Notes to Condensed Consolidated Financial Statements (unaudited) (continued)

Product sales are recorded net of the provision for discounts, including chargebacks, which are customer discounts that occur when a contracted customer purchases through an intermediary wholesale purchaser, and rebates that are owed based upon definitive contractual agreements or legal requirements with private sector and public sector (Medicaid and Medicare Part D) benefit providers, after the final dispensing of the product by a pharmacy to a benefit plan participant. These discounts, in the aggregate, reduced U.S. sales by $3.4 billion and $3.0 billion for the three months ended September 30, 2020 and 2019, respectively, and $9.6 billion and $8.6 billion for the nine months ended September 30, 2020 and 2019, respectively.

Consolidated sales by geographic area where derived are as follows:

			Three Months Ended September 30,												Nine Months Ended September 30,
($ in millions)			2020						2019						2020						2019
United States			$	5,625					$	5,573					$	15,396					$	15,320
Europe, Middle East and Africa			3,454						3,189						10,059						9,452
China			1,016						914						2,715						2,423
Japan			828						919						2,506						2,639
Asia Pacific (other than China and Japan)			735						756						2,129						2,217
Latin America			604						671						1,670						1,889
Other			289						375						1,004						1,032
			$	12,551					$	12,397					$	35,479					$	34,972

A reconciliation of segment profits to Income before taxes is as follows:

			Three Months Ended September 30,												Nine Months Ended September 30,
($ in millions)			2020						2019						2020						2019
Segment profits:
Pharmaceutical segment			$	7,974					$	7,747					$	22,010					$	21,437
Animal Health segment			451						423						1,336						1,243
Other segment			(1)						(2)						1						(2)
Total segment profits			8,424						8,168						23,347						22,678
Other profits			(12)						101						188						226
Unallocated:
Interest income			9						61						48						225
Interest expense			(203)						(231)						(624)						(674)
Depreciation and amortization			(395)						(382)						(1,173)						(1,169)
Research and development			(3,272)						(3,110)						(7,364)						(7,045)
Amortization of purchase accounting adjustments			(285)						(329)						(879)						(1,105)
Restructuring costs			(114)						(232)						(269)						(444)
Other unallocated, net			(724)						(1,699)						(2,490)						(4,019)
			$	3,428					$	2,347					$	10,784					$	8,673

Pharmaceutical segment profits are comprised of segment sales less standard costs, as well as selling, general and administrative expenses directly incurred by the segment. Animal Health segment profits are comprised of segment sales, less all cost of sales, as well as selling, general and administrative expenses and research and development costs directly incurred by the segment. For internal management reporting presented to the chief operating decision maker, Merck does not allocate the remaining cost of sales not included in segment profits as described above, research and development expenses incurred in Merck Research Laboratories, the Company’s research and development division that focuses on human health-related activities, or general and administrative expenses, nor the cost of financing these activities. Separate divisions maintain responsibility for monitoring and managing these costs, including depreciation related to fixed assets utilized by these divisions and, therefore, they are not included in segment profits. In addition, costs related to restructuring activities, as well as the amortization of purchase accounting adjustments are not allocated to segments.

Other profits are primarily comprised of miscellaneous corporate profits, as well as operating profits related to third-party manufacturing sales.

Other unallocated, net, includes expenses from corporate and manufacturing cost centers, goodwill and other intangible asset impairment charges, gains or losses on sales of businesses, expense or income related to changes in the estimated fair value measurement of liabilities for contingent consideration, and other miscellaneous income or expense items.

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Notes to Condensed Consolidated Financial Statements (unaudited) (continued)

Item 2. Management’s Discussion and Analysis of Financial Condition and Results of Operations

Planned Spin-Off of Women’s Health, Biosimilars and Established Brands into New Company

In February 2020, Merck announced its intention to spin-off products from its women’s health, biosimilars and established brands businesses into a new, independent, publicly traded company named Organon & Co. (Organon) through a distribution of Organon’s publicly traded stock to Company shareholders. The distribution is expected to qualify as tax-free to the Company and its shareholders for U.S. federal income tax purposes. The established brands included in the transaction consist of dermatology, non-opioid pain management, respiratory, and select cardiovascular products including Zetia (ezetimibe) and Vytorin (ezetimibe and simvastatin), as well as the rest of Merck’s diversified brands franchise. Merck’s existing research pipeline programs will continue to be owned and developed within Merck as planned. Organon will have development capabilities initially focused on late-stage development and life-cycle management and is expected over time to develop research capabilities in selected therapeutic areas. The spin-off is expected to be completed in the second quarter of 2021, subject to market and certain other conditions. Subsequent to the spin-off, the historical results of the women’s health, biosimilars and established brands businesses will be reflected as discontinued operations in the Company’s consolidated financial statements.

Recent Developments

Management

In October 2020, Merck announced that Dr. Roger M. Perlmutter will be retiring as Executive Vice President and President, Merck Research Laboratories (MRL). Dr. Perlmutter will be succeeded by Dr. Dean Y. Li, effective January 1, 2021. Dr. Perlmutter will remain as Non-Executive Chairman, MRL through June 30, 2021 to facilitate a seamless transition.

Business Developments

Below is a summary of significant 2020 business development activity. See Note 2 to the condensed consolidated financial statements for additional information.

In November 2020, Merck and VelosBio, Inc. (VelosBio) announced that the companies had entered into a definitive agreement pursuant to which Merck, through a subsidiary, will acquire all outstanding shares of VelosBio for $2.75 billion, subject to certain customary adjustments. VelosBio is a privately held clinical-stage biopharmaceutical company committed to developing first-in-class cancer therapies targeting receptor tyrosine kinase-like orphan receptor 1 (ROR1). VelosBio’s lead investigational candidate is VLS-101, an antibody-drug conjugate targeting ROR1 that is currently being evaluated in a Phase 1 and a Phase 2 clinical trial for the treatment of patients with hematologic malignancies and solid tumors, respectively. The closing of the transaction, which is subject to approval under the Hart-Scott-Rodino Antitrust Improvements Act and other customary conditions, is expected by the end of 2020.

In September 2020, Merck and Seagen Inc. (Seagen, formerly known as Seattle Genetics, Inc.) announced an oncology collaboration to globally develop and commercialize Seagen’s ladiratuzumab vedotin (MK-6440), an investigational antibody-drug conjugate targeting LIV-1, which is currently in Phase 2 clinical trials for breast cancer and other solid tumors. The companies will equally share profits worldwide. Under the terms of the agreement, Merck made an upfront payment of $600 million and a $1.0 billion equity investment in 5 million shares of Seagen common stock at a price of $200 per share. The closing of the equity investment occurred in October 2020. Seagen is also eligible to receive future contingent milestone payments dependent upon the achievement of certain developmental and sales-based milestones.

Concurrent with the above transaction, Seagen granted Merck an exclusive license to commercialize Tukysa (tucatinib), a small molecule tyrosine kinase inhibitor, for the treatment of HER2-positive cancers, in Asia, the Middle East and Latin America and other regions outside of the United States, Canada and Europe. Under the terms of the agreement, Merck made upfront payments aggregating $210 million. Seagen is also eligible to receive future contingent regulatory approval milestones and will receive tiered royalties on sales of Tukysa in Merck’s territories.

Additionally in September 2020, Merck acquired a biologics manufacturing facility located in Dunboyne, Ireland from Takeda Pharmaceutical Company Limited for €256 million ($302 million).

In July 2020, Merck acquired the U.S. rights to Sentinel Flavor Tabs and Sentinel Spectrum Chews from Virbac Corporation for $410 million. Sentinel products provide protection against common parasites in dogs.

Also, in July 2020, Merck and Ridgeback Biotherapeutics LP (Ridgeback Bio), a closely held biotechnology company, closed a collaboration agreement to develop molnupiravir (MK-4482, formerly known as EIDD-2801), an orally available antiviral candidate currently in clinical development for the treatment of patients with COVID-19. Merck gained exclusive worldwide rights to develop and commercialize molnupiravir and related molecules. Under the terms of the agreement, Ridgeback Bio received an upfront payment and also is eligible to receive future contingent payments dependent upon the achievement of certain developmental and regulatory approval milestones, as well as a share of the net profits of molnupiravir and related molecules, if approved.

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In June 2020, Merck acquired privately held Themis Bioscience GmbH (Themis), a company focused on vaccines and immune-modulation therapies for infectious diseases and cancer for $366 million. Merck may make additional contingent payments dependent upon the achievement of certain developmental, regulatory approval and commercial milestones. The acquisition builds upon an ongoing collaboration between the two companies to develop vaccine candidates using the measles virus vector platform and is expected to accelerate the development of the COVID-19 vaccine candidate (V591), which is currently in Phase 1 clinical development.

In May 2020, Merck and the International AIDS Vaccine Initiative, Inc. (IAVI), a nonprofit scientific research organization dedicated to addressing urgent, unmet global health challenges, announced a new collaboration to develop V590, an investigational vaccine against SARS-CoV-2 being studied for the prevention of COVID-19, which is currently in Phase 1 clinical development. Under the terms of the agreement, Merck made an upfront payment of $6.5 million and may make additional contingent payments dependent upon the achievement of certain sales-based milestones, as well as royalties.

In January 2020, Merck acquired ArQule, Inc. (ArQule), a publicly traded biopharmaceutical company focused on kinase inhibitor discovery and development for the treatment of patients with cancer and other diseases, for total consideration of $2.7 billion. ArQule’s lead investigational candidate, MK-1026 (formerly known as ARQ 531), is a novel, oral Bruton’s tyrosine kinase (BTK) inhibitor currently being evaluated for the treatment of B-cell malignancies.

Coronavirus Disease 2019 (COVID-19) Update

Overall, in response to the COVID-19 pandemic, Merck is focused on protecting the safety of its employees, ensuring that its supply of medicines and vaccines reaches its patients, contributing its scientific expertise to the development of vaccine and antiviral approaches, and supporting health care providers and Merck’s communities. Although COVID-19-related disruptions to patients’ ability to access health care providers negatively affected results for the third quarter and first nine months of 2020, Merck remains confident in the fundamental underlying demand for its products and its prospects for long-term growth.

In the third quarter of 2020, the negative impact of the COVID-19 pandemic to Merck’s Pharmaceutical sales was estimated to be approximately $475 million. The negative impact to Animal Health sales was immaterial. The negative impact to sales in the first nine months of 2020 was approximately $2.0 billion for the Pharmaceutical segment and $50 million for the Animal Health segment. Merck assumes that the majority of the negative impact from the COVID-19 pandemic occurred in the second quarter of 2020. However, the Company expects some residual negative impacts in the fourth quarter, largely in Europe and certain emerging markets. In addition, the phasing of the recovery of Gardasil 9 (Human Papillomavirus 9-valent Vaccine, Recombinant) demand is slower than originally anticipated, in particular in the United States due to lower back-to-school demand. Accordingly, for the full-year 2020, including the impact for the first nine months, Merck expects an unfavorable impact to sales of approximately $2.35 billion (excluding the impact of foreign exchange) due to the COVID-19 pandemic, comprised of approximately $2.3 billion for Pharmaceutical revenue and approximately $50 million for Animal Health revenue.

Roughly two-thirds of Merck’s Pharmaceutical revenue is comprised of physician-administered products, which, despite strong underlying demand, were affected by social distancing measures, fewer well visits and delays in elective surgeries due to the COVID-19 pandemic. These impacts, as well as the prioritization of COVID-19 patients at health care providers, have resulted in reduced administration of many of the Company’s human health products, in particular for its vaccines, including Gardasil 9, as well as for Keytruda (pembrolizumab) and Implanon/Nexplanon (etonogestrel implant). Access to healthcare providers remains reduced, although improved from the second quarter. Merck anticipates reduced demand for its physician-administered products while pandemic-related access measures remain in place. In addition, declines in elective surgeries negatively affected the demand for Bridion (sugammadex) Injection in the year-to-date period. Sales of Pneumovax 23 (pneumococcal vaccine polyvalent) increased due to heightened awareness of pneumococcal vaccination during the COVID-19 pandemic and ahead of flu season.

Operating expenses were positively affected in the third quarter and first nine months of 2020 by approximately $115 million and $540 million, respectively, primarily driven by lower promotional and selling costs, as well as lower research and development expenses, net of investments in COVID-19-related antiviral and vaccine research programs. For the full-year 2020, Merck expects a net favorable impact to operating expenses of approximately $625 million reflecting continued lower spending due to the COVID-19 pandemic, partially offset by spending on COVID-19-related antiviral and vaccine research programs.

Pricing

Global efforts toward health care cost containment continue to exert pressure on product pricing and market access worldwide. In the United States, pricing pressure continues on many of the Company’s products. Changes to the U.S. health care system as part of health care reform, as well as increased purchasing power of entities that negotiate on behalf of Medicare, Medicaid, and private sector beneficiaries, have contributed to pricing pressure. In several international markets, government-mandated pricing actions have reduced prices of generic and patented drugs. In addition, the Company’s revenue

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performance in the first nine months of 2020 was negatively affected by other cost-reduction measures taken by governments and other third-parties to lower health care costs. The Company anticipates all of these actions and additional actions in the future will continue to negatively affect revenue performance.

Operating Results

Sales

			Three Months Ended September 30,																		% Change Excluding Foreign Exchange						Nine Months Ended September 30,																		% Change Excluding Foreign Exchange
($ in millions)			2020						2019						% Change												2020						2019						% Change
United States			$	5,625					$	5,573					1		%				1		%				$	15,396					$	15,320					—		%				—		%
International			6,926						6,824						1		%				4		%				20,084						19,652						2		%				5		%
Total			$	12,551					$	12,397					1		%				2		%				$	35,479					$	34,972					1		%				3		%

U.S. plus international may not equal total due to rounding.

Worldwide sales were $12.6 billion and $35.5 billion for the third quarter and first nine months of 2020, respectively, representing growth of 1% compared with the same prior year periods. Sales growth in both periods was primarily driven by higher sales in the oncology franchise reflecting strong growth of Keytruda, as well as increased alliance revenue from Lynparza (olaparib) and Lenvima (lenvatinib). Also contributing to revenue growth were higher sales of certain vaccines, including Pneumovax 23, and higher sales of certain hospital acute care products, including Prevymis (letermovir) and Bridion. Higher sales of Animal Health products also contributed to revenue growth in the third quarter and first nine months of 2020.

Sales growth in both periods was partially offset by the ongoing effects of generic competition for certain products including women’s health product NuvaRing (etonogestrel/ethinyl estradiol vaginal ring), hospital acute care product Noxafil (posaconazole), oncology products Emend (aprepitant)/Emend (fosaprepitant dimeglumine) for Injection, cardiovascular products Zetia and Vytorin, as well as products within the diversified brands franchise. The diversified brands franchise includes certain products that are approaching the expiration of their marketing exclusivity or that are no longer protected by patents in developed markets. Lower sales of certain vaccines including human papillomavirus (HPV) vaccines Gardasil (Human Papillomavirus Quadrivalent [Types 6,11,16 and 18] Vaccine, Recombinant)/Gardasil 9 and pediatric vaccines ProQuad (Measles, Mumps, Rubella and Varicella Virus Vaccine Live), M-M-R II (Measles, Mumps and Rubella Virus Vaccine Live) and Varivax (Varicella Virus Vaccine Live), as well as lower sales of virology products Zepatier (elbasvir and grazoprevir) and Isentress/Isentress HD (raltegravir) also partially offset revenue growth in the third quarter and first nine months of 2020. As discussed above, the COVID-19 pandemic unfavorably affected sales in the third quarter and first nine months of 2020.

See Note 17 to the condensed consolidated financial statements for details on sales of the Company’s products. A discussion of performance for select products in the franchises follows.

Pharmaceutical Segment

Oncology

			Three Months Ended September 30,																		% Change Excluding Foreign Exchange						Nine Months Ended September 30,																		% Change Excluding Foreign Exchange
($ in millions)			2020						2019						% Change												2020						2019						% Change
Keytruda			$	3,715					$	3,070					21		%				21		%				$	10,387					$	7,973					30		%				31		%
Alliance Revenue - Lynparza (1)			196						123						59		%				58		%				519						313						66		%				67		%
Alliance Revenue - Lenvima (1)			142						109						30		%				29		%				421						280						50		%				50		%
Emend			39						98						(60)		%				(59)		%				115						336						(66)		%				(65)		%

(1) Alliance revenue represents Merck’s share of profits, which are product sales net of cost of sales and commercialization costs (see Note 3 to the condensed consolidated financial statements).

Keytruda is an anti-PD-1 (programmed death receptor-1) therapy that has been approved as monotherapy for the treatment of certain patients with cervical cancer, classical Hodgkin lymphoma (cHL), cutaneous squamous cell carcinoma (cSCC), esophageal cancer, gastric or gastroesophageal junction adenocarcinoma, head and neck squamous cell carcinoma (HNSCC), hepatocellular carcinoma (HCC), non-small-cell lung cancer (NSCLC), small-cell lung cancer (SCLC), melanoma, Merkel cell carcinoma, microsatellite instability-high (MSI-H) or mismatch repair deficient cancer, primary mediastinal large B-cell lymphoma (PMBCL), and urothelial carcinoma. Keytruda is also approved for the treatment of certain patients in combination with chemotherapy for metastatic squamous and nonsquamous NSCLC, in combination with chemotherapy for HNSCC, in combination with axitinib for renal cell carcinoma (RCC), and in combination with Lenvima for endometrial

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carcinoma. The Keytruda clinical development program includes studies across a broad range of cancer types (see “Research and Development” below).

In January 2020, the U.S. Food and Drug Administration (FDA) approved Keytruda as monotherapy for the treatment of certain patients with Bacillus Calmette-Guerin (BCG)-unresponsive, high-risk, non-muscle invasive bladder cancer (NMIBC) based on the results of the KEYNOTE-057 trial.

In April 2020, the FDA granted accelerated approval for an additional recommended dosage of 400 mg every six weeks (Q6W) for Keytruda across all adult indications, including monotherapy and combination therapy. This new dosage option is available in addition to the current dose of 200 mg every three weeks (Q3W).

In June 2020, the FDA granted accelerated approval for Keytruda as monotherapy for the treatment of adult and pediatric patients with unresectable or metastatic tumor mutational burden-high (TMB-H) (≥10 mutations/megabase) solid tumors, as determined by an FDA-approved test, that have progressed following prior treatment and who have no satisfactory alternative treatment options based in part on the results of the KEYNOTE-158 trial.

Also in June 2020, the FDA approved Keytruda as monotherapy both for the treatment of patients with recurrent or metastatic cSCC that is not curable by surgery or radiation based on data from the Phase 2 KEYNOTE-629 trial and for the first-line treatment of patients with unresectable or metastatic MSI-H or mismatch repair deficient colorectal cancer based on results from the Phase 3 KEYNOTE-177 trial.

In October 2020, the FDA approved an expanded label for Keytruda as monotherapy for the treatment of adult patients with relapsed or refractory cHL. The approval is based on results from the Phase 3 KEYNOTE-204 trial in which Keytruda significantly reduced the risk of disease progression or death compared to brentuximab vedotin. The FDA also approved an updated pediatric indication for Keytruda for the treatment of pediatric patients with refractory cHL or cHL that has relapsed after two or more lines of therapy. Keytruda was previously approved under the FDA’s accelerated approval process for the treatment of adult and pediatric patients with refractory cHL, or who have relapsed after three or more prior lines of therapy based on data from the KEYNOTE-087 trial. In accordance with accelerated approval regulations, continued approval was contingent upon verification and description of clinical benefit; these accelerated approval requirements have been fulfilled with the data from KEYNOTE-204.

In June 2020, Keytruda was approved by the National Medical Products Administration (NMPA) in China as monotherapy for the second-line treatment of patients with locally advanced or metastatic esophageal squamous cell carcinoma (ESCC) whose tumors express PD-L1 (Combined Positive Score [CPS] ≥10). This indication was granted based on the Phase 3 KEYNOTE-181 trial, including data from an extension of the global study in Chinese patients.

In August 2020, Keytruda was approved by the Japan Pharmaceuticals and Medical Devices Agency (PMDA) as monotherapy for the treatment of patients whose tumors are PD-L1-positive, and have radically unresectable, advanced or recurrent ESCC who have progressed after chemotherapy. The approval was based on results from the Phase 3 KEYNOTE-181 trial. Additionally, Keytruda was approved by the Japan PMDA for use at an additional recommended dosage of 400 mg Q6W, including monotherapy and combination therapy. This new dosage option is available in addition to the current dose of 200 mg Q3W.

Global sales of Keytruda grew 21% and 30% in the third quarter and first nine months of 2020, respectively. Sales growth in both periods was driven by higher demand as the Company continues to launch Keytruda with multiple new indications globally, although the COVID-19 pandemic had a dampening effect on growing demand. Sales in the United States continue to build across the multiple approved indications, in particular for the treatment of NSCLC as monotherapy, and in combination with chemotherapy for both nonsquamous and squamous metastatic NSCLC, along with uptake in the RCC, adjuvant melanoma, HNSCC, bladder cancer and endometrial carcinoma indications. Uptake of the Q6W dosing regimen in the United States benefited sales in 2020. Keytruda sales growth in international markets was driven by continued uptake in approved indications, particularly in the European Union (EU). Sales growth in the third quarter and first nine months of 2020 was partially offset by declines in Japan due to pricing. Pursuant to a re-pricing rule, the Japanese government reduced the price of Keytruda by 17.5% effective February 2020. Additionally, Keytruda was subject to another price reduction of 20.9% in April 2020 under a provision of the Japanese pricing rules.

Lynparza, an oral poly (ADP-ribose) polymerase (PARP) inhibitor being developed as part of a collaboration with AstraZeneca PLC (AstraZeneca) (see Note 3 to the condensed consolidated financial statements), is approved for the treatment of certain types of advanced ovarian, breast, pancreatic and prostate cancers. Alliance revenue related to Lynparza increased 59% and 66% in the third quarter and first nine months of 2020, respectively. Sales growth in both periods was largely driven by continued uptake across the multiple approved indications in the United States, the EU and China. In May 2020, the FDA approved Lynparza in combination with bevacizumab as a first-line maintenance treatment of certain adult patients with advanced epithelial ovarian, fallopian tube or primary peritoneal cancer who are in complete or partial response to first-line platinum-based chemotherapy based on the results from the Phase 3 PAOLA-1 trial. In November 2020, Lynparza was

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approved in the EU for the maintenance treatment of adult patients with advanced high-grade epithelial ovarian, fallopian tube or primary peritoneal cancer who are in complete or parital response following completion of first-line platinum-based chemotherapy in combination with bevacizumab and whose cancer is associated with homologous recombination deficiency (HRD)-positive status defined by either a breast cancer susceptibility gene 1/2 (BRCA1/2) mutation and/or genomic instability based on the results from the PAOLA-1 trial. Also in May 2020, the FDA approved Lynparza for the treatment of adult patients with deleterious or suspected deleterious germline or somatic homologous recombination repair (HRR) gene-mutated metastatic castration-resistant prostate cancer (mCRPC) who have progressed following prior treatment with enzalutamide or abiraterone based on positive results from the Phase 3 PROfound trial. In November 2020, Lynparza was approved in the EU as monotherapy for the treatment of adult patients with mCRPC and BRCA1/2 mutations (germline and/or somatic) who have progressed following a prior therapy that included a new hormonal agent based on the PROfound trial. In July 2020, Lynparza was approved in the EU as a monotherapy for the maintenance treatment of adult patients with germline BRCA1/2 mutations who have metastatic adenocarcinoma of the pancreas and have not progressed after a minimum of 16 weeks of platinum treatment within a first-line chemotherapy regimen based on the results from the Phase 3 POLO trial.

Lenvima, an oral receptor tyrosine kinase inhibitor being developed as part of a collaboration with Eisai Co., Ltd. (Eisai) (see Note 3 to the condensed consolidated financial statements), is approved for the treatment of certain types of thyroid cancer, HCC, in combination with everolimus for certain patients with RCC, and in combination with Keytruda for the treatment of certain patients with endometrial carcinoma. Alliance revenue related to Lenvima grew 30% and 50% in the third quarter and first nine months of 2020, respectively. Sales growth in both periods was primarily due to higher demand in the United States, China and the EU.

Global sales of Emend, for the prevention of chemotherapy-induced nausea and vomiting, declined 60% and 66% in the third quarter and first nine months of 2020, respectively. The sales declines were primarily driven by lower demand and pricing in the United States due to generic competition, including recent generic competition for Emend for Injection following U.S. patent expiry in September 2019. Also contributing to the sales declines in the third quarter and first nine months of 2020 was lower demand in the EU as a result of generic competition for the oral formulation of Emend following loss of market exclusivity in May 2019. U.S. market exclusivity for the oral formulation of Emend previously expired in 2015. Generic competition for Emend for Injection in Japan following loss of exclusivity also contributed to the sales declines in the third quarter and first nine months of 2020. Emend for Injection lost market exclusivity in major European markets in August 2020. The Company anticipates that sales of Emend for Injection in these markets will decline significantly in future periods.

In April 2020, the FDA approved Koselugo (selumetinib) for the treatment of pediatric patients two years of age and older with neurofibromatosis type 1 (NF1) who have symptomatic, inoperable plexiform neurofibromas (PN). The FDA approval is based on positive results from the National Cancer Institute (NCI) Cancer Therapy Evaluation Program (CTEP)-sponsored Phase 2 SPRINT Stratum 1 trial coordinated by the NCI’s Center for Cancer Research, Pediatric Oncology Branch. This is the first regulatory approval of a medicine for the treatment of NF1 PN, a rare and debilitating genetic condition. Koselugo is being jointly developed and commercialized with AstraZeneca globally (see Note 3 to the condensed consolidated financial statements).

Vaccines

			Three Months Ended September 30,																		% Change Excluding Foreign Exchange						Nine Months Ended September 30,																		% Change Excluding Foreign Exchange
($ in millions)			2020						2019						% Change												2020						2019						% Change
Gardasil/Gardasil 9			$	1,187					$	1,320					(10)		%				(10)		%				$	2,941					$	3,044					(3)		%				(2)		%
ProQuad			218						232						(6)		%				(6)		%				507						588						(14)		%				(14)		%
M-M-R II			115						121						(5)		%				(6)		%				287						443						(35)		%				(35)		%
Varivax			243						270						(10)		%				(9)		%				595						763						(22)		%				(21)		%
Pneumovax 23			375						237						58		%				58		%				748						592						26		%				27		%

Worldwide sales of Gardasil/Gardasil 9, vaccines to help prevent certain cancers and other diseases caused by certain types of HPV, declined 10% and 3% in the third quarter and first nine months of 2020, respectively, primarily due to lower demand in the United States and Hong Kong, SAR, PRC attributable to the COVID-19 pandemic, partially offset by higher volumes in China and in the EU.

The Company anticipates that in the fourth quarter of 2020 it will replenish the doses of Gardasil 9 borrowed from the U.S. Centers for Disease Control and Prevention (CDC) Pediatric Vaccine Stockpile in the fourth quarter of 2019. The replenishment will result in the recognition of approximately $120 million in sales and a reversal of the related liability.

In June 2020, the FDA approved an expanded indication for Gardasil 9 for the prevention of oropharyngeal and other head and neck cancers caused by HPV Types 16, 18, 31, 33, 45, 52, and 58. The oropharyngeal and head and neck

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cancer indication was approved under accelerated approval based on effectiveness in preventing HPV-related anogenital disease.

In July 2020, Silgard 9 aqueous suspension for intramuscular injection syringes (recombinant adsorbed 9-valent Human Papillomavirus virus-like particles vaccine) were approved for use in women and girls by the Ministry of Health, Labor and Welfare in Japan.

Global sales of ProQuad, a pediatric combination vaccine to help protect against measles, mumps, rubella and varicella, declined 6% and 14% in the third quarter and first nine months of 2020, respectively, primarily due to lower demand in the United States resulting from the COVID-19 pandemic, partially offset by higher pricing.

Worldwide sales of M‑M‑R II, a vaccine to help protect against measles, mumps and rubella, declined 35% in the first nine months of 2020 primarily driven by lower demand in the United States resulting from fewer measles outbreaks in 2020 compared with 2019, coupled with the unfavorable impact of the COVID-19 pandemic, partially offset by higher pricing. Additionally, the sales decline in the first nine months of 2020 reflects lower demand in Brazil.

Global sales of Varivax, a vaccine to help prevent chickenpox (varicella), declined 10% and 22% in the third quarter and first nine months of 2020, respectively. The sales declines reflect lower demand in the United States resulting from the COVID-19 pandemic, partially offset by higher pricing. The sales decline in the first nine months of 2020 was also attributable to lower government tenders in Brazil.

Worldwide sales of Pneumovax 23, a vaccine to help prevent pneumococcal disease, grew 58% and 26% in the third quarter and first nine months of 2020, respectively, primarily due to higher volumes in the United States and in the EU attributable in part to heightened awareness of pneumococcal vaccination during the COVID-19 pandemic and ahead of flu season. Higher pricing in the United States also contributed to sales growth in the third quarter and first nine months of 2020.

Hospital Acute Care

			Three Months Ended September 30,																		% Change Excluding Foreign Exchange						Nine Months Ended September 30,																		% Change Excluding Foreign Exchange
($ in millions)			2020						2019						% Change												2020						2019						% Change
Bridion			$	320					$	284					13		%				13		%				$	843					$	817					3		%				4		%
Noxafil			79						177						(55)		%				(55)		%				247						560						(56)		%				(55)		%
Prevymis			77						45						72		%				69		%				200						115						74		%				74		%
Cubicin			39						52						(26)		%				(25)		%				116						207						(44)		%				(43)		%

Worldwide sales of Bridion, for the reversal of two types of neuromuscular blocking agents used during surgery, grew 13% and 3% in the third quarter and first nine months of 2020, respectively, primarily attributable to higher demand in the United States. Fewer elective surgeries as a result of the COVID-19 pandemic unfavorably affected demand in 2020.

Global sales of Noxafil, for the prevention of invasive fungal infections, declined 55% and 56% in the third quarter and first nine months of 2020, respectively, primarily due to generic competition in the United States and in the EU. The patents that provided U.S. market exclusivity for certain forms of Noxafil representing the majority of U.S. Noxafil sales expired in July 2019. Additionally, the patent for Noxafil expired in a number of major European markets in December 2019. Accordingly, the Company is experiencing volume and pricing declines in Noxafil sales in these markets as a result of generic competition and expects the declines to continue.

Worldwide sales of Prevymis, a medicine for prophylaxis (prevention) of cytomegalovirus (CMV) infection and disease in adult CMV-seropositive recipients of an allogenic hematopoietic stem cell transplant, grew 72% and 74% in the third quarter and first nine months of 2020, respectively, due to continued uptake since launch in the EU and in the United States.

Global sales of Cubicin (daptomycin for injection), an I.V. antibiotic for complicated skin and skin structure infections or bacteremia when caused by designated susceptible organisms, declined 26% and 44% in the third quarter and first nine months of 2020, respectively, primarily due to ongoing generic competition in the EU and in the United States.

In June 2020, the FDA approved a supplemental New Drug Application (NDA) for Recarbrio (imipenem, cilastatin, and relebactam) for the treatment of patients 18 years of age and older with hospital-acquired bacterial pneumonia and ventilator-associated bacterial pneumonia (HABP/VABP), caused by certain susceptible Gram-negative microorganisms.

Zerbaxa (ceftolozane and tazobactam) is indicated for the treatment of HABP/VABP caused by certain susceptible Gram-negative microorganisms, and for the treatment of certain complicated urinary tract and intra-abdominal infections. The COVID-19 pandemic is unfavorably affecting sales of Zerbaxa, particularly in the United States. An increased focus on more stringent cleaning protocols at hospitals, along with visitor restrictions, have reduced patients’ exposure to developing HABP/

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VABP, resulting in a smaller population of patients that need to be treated with Zerbaxa. These factors resulted in lower cash flow forecasts for Zerbaxa in the United States, which constituted a triggering event requiring the evaluation of the Zerbaxa intangible asset for impairment. Although the “step one” impairment test that was performed indicated that the intangible asset related to Zerbaxa remains recoverable, in the event that these trends depress sales of Zerbaxa to a greater extent than anticipated by the Company, or in the event other circumstances arise that further reduce global cash flow projections for Zerbaxa, the Company may record an intangible asset impairment charge in the future and such charge could be material. The carrying value of Zerbaxa was $2.2 billion at September 30, 2020.

Immunology

			Three Months Ended September 30,																		% Change Excluding Foreign Exchange						Nine Months Ended September 30,																		% Change Excluding Foreign Exchange
($ in millions)			2020						2019						% Change												2020						2019						% Change
Simponi			$	209					$	203					3		%				—		%				$	615					$	625					(2)		%				(1)		%
Remicade			82						101						(19)		%				(20)		%				242						322						(25)		%				(24)		%

Sales of Simponi (golimumab), a once-monthly subcutaneous treatment for certain inflammatory diseases (marketed by the Company in Europe, Russia and Turkey), declined 2% in the first nine month of 2020 primarily driven by lower demand in the EU due to the uptake of biosimilars for a competing product, partially offset by the timing of shipments in Russia.

Sales of Remicade (infliximab), a treatment for inflammatory diseases (marketed by the Company in Europe, Russia and Turkey), declined 19% and 25% in the third quarter and first nine months of 2020, respectively, driven by ongoing biosimilar competition in the Company’s marketing territories in Europe. The Company lost market exclusivity for Remicade in major European markets in 2015 and no longer has market exclusivity in any of its marketing territories. The Company is experiencing pricing and volume declines in these markets as a result of biosimilar competition and expects the declines to continue.

Virology

			Three Months Ended September 30,																		% Change Excluding Foreign Exchange						Nine Months Ended September 30,																		% Change Excluding Foreign Exchange
($ in millions)			2020						2019						% Change												2020						2019						% Change
Isentress/Isentress HD			$	205					$	250					(18)		%				(18)		%				$	646					$	752					(14)		%				(12)		%
Zepatier			28						83						(67)		%				(67)		%				122						304						(60)		%				(59)		%

Global combined sales of Isentress/Isentress HD, an HIV integrase inhibitor for use in combination with other antiretroviral agents for the treatment of HIV-1 infection, declined 18% and 14% in the third quarter and first nine months of 2020, respectively, primarily driven by competitive pressure in the United States and in the EU, as well as the timing of shipments in Brazil.

Global sales of Zepatier, a treatment for adult patients with chronic hepatitis C virus genotype (GT) 1 or GT4 infection, declined 67% and 60% in the third quarter and first nine months of 2020, respectively, driven by lower demand globally due to competition and declining patient volumes, coupled with the impact of the COVID-19 pandemic.

Cardiovascular

			Three Months Ended September 30,																		% Change Excluding Foreign Exchange						Nine Months Ended September 30,																		% Change Excluding Foreign Exchange
($ in millions)			2020						2019						% Change												2020						2019						% Change
Zetia/Vytorin			$	150					$	204					(27)		%				(26)		%				$	523					$	674					(22)		%				(21)		%
Atozet			111						97						14		%				12		%				348						283						23		%				25		%
Rosuzet			32						32						1		%				—		%				94						97						(3)		%				(1)		%
Alliance Revenue - Adempas (1)			83						50						67		%				67		%				216						144						50		%				50		%
Adempas			55						57						(5)		%				(7)		%				167						158						6		%				6		%

(1) Alliance revenue represents Merck’s share of profits from sales in Bayer’s marketing territories, which are product sales net of cost of sales and commercialization costs (see Note 3 to the condensed consolidated financial statements).

Combined global sales of Zetia (marketed in most countries outside the United States as Ezetrol) and Vytorin (marketed outside the United States as Inegy), medicines for lowering LDL cholesterol, declined 27% in the third quarter of 2020, primarily due to lower sales of Ezetrol in Japan. The patent that provided market exclusivity for Ezetrol in Japan expired in September 2019 and generic competition began in June 2020. Accordingly, the Company is experiencing a rapid and

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substantial decline in Ezetrol sales in Japan and expects the decline to continue. Higher demand for Ezetrol in China partially offset the sales decline in the third quarter of 2020. Combined global sales of Zetia and Vytorin declined 22% in the first nine months of 2020 primarily due to generic competition for Ezetrol and Inegy in the EU and Ezetrol in Japan. The EU patents for Ezetrol and Inegy expired in April 2018 and April 2019, respectively. The sales decline in the first nine months of 2020 was also attributable to lower pricing following loss of exclusivity in Australia in 2018. Higher demand for Ezetrol in China partially offset the sales decline in the first nine months of 2020.

Sales of Atozet (ezetimibe and atorvastatin) (marketed outside of the United States), a medicine for lowering LDL cholesterol, grew 14% and 23% in the third quarter and first nine months of 2020, respectively, primarily due to higher demand in most markets, particularly in the EU, Japan and other countries in the Asia Pacific region.

Adempas (riociguat), a cardiovascular drug for the treatment of pulmonary arterial hypertension, is part of a worldwide clinical development collaboration with Bayer AG (Bayer) to market and develop soluble guanylate cyclase (sGC) modulators including Adempas (see Note 3 to the condensed consolidated financial statements). Revenue from Adempas includes Merck’s share of profits from the sale of Adempas in Bayer’s marketing territories, which grew 67% and 50% in the third quarter and first nine months of 2020, respectively, as well as sales in Merck’s marketing territories, which declined 5% in the third quarter and grew 6% in the first nine months of 2020.

Diabetes

			Three Months Ended September 30,																		% Change Excluding Foreign Exchange						Nine Months Ended September 30,																		% Change Excluding Foreign Exchange
($ in millions)			2020						2019						% Change												2020						2019						% Change
Januvia/Janumet			$	1,327					$	1,311					1		%				2		%				$	3,948					$	4,106					(4)		%				(3)		%

Worldwide combined sales of Januvia (sitagliptin) and Janumet (sitagliptin/metformin HCl), medicines that help lower blood sugar levels in adults with type 2 diabetes, grew 1% in the third quarter of 2020 driven primarily by higher demand in certain international markets, particularly in China, partially offset by continued pricing pressure in the United States. Global combined sales of Januvia and Janumet declined 4% in the first nine months of 2020. The decline was primarily due to continued pricing pressure in the United States and lower demand in the EU, partially offset by higher demand in certain international markets, particularly in China. The Company expects U.S. pricing pressure to continue. The patents that provide market exclusivity for Januvia and Janumet in the United States expire in July 2022 (although six-month pediatric exclusivity may extend this date). The patent that provides market exclusivity for Januvia in the EU expires in July 2022 (although pediatric exclusivity has recently been granted which may extend this date to September 2022 and the Company is applying in individual countries for the extensions). The supplementary patent certificate that provides market exclusivity for Janumet in the EU expires in April 2023. The Company anticipates sales of Januvia and Janumet in these markets will decline substantially after these patent expiries.

Women’s Health 

			Three Months Ended September 30,																		% Change Excluding Foreign Exchange						Nine Months Ended September 30,																		% Change Excluding Foreign Exchange
($ in millions)			2020						2019						% Change												2020						2019						% Change
Implanon/Nexplanon			$	189					$	199					(5)		%				(4)		%				$	515					$	581					(11)		%				(10)		%
NuvaRing			58						241						(76)		%				(76)		%				184						700						(74)		%				(73)		%

Global sales of Implanon/Nexplanon, a single-rod subdermal contraceptive implant, declined 5% in the third quarter of 2020 primarily driven by lower demand in Latin America. Worldwide sales of Implanon/Nexplanon declined 11% in the first nine months of 2020 primarily due to lower demand in the United States and in the EU resulting from the COVID-19 pandemic.

Worldwide sales of NuvaRing, a vaginal contraceptive product, declined 76% and 74% in the third quarter and first nine months of 2020, respectively, due to generic competition in the United States. The patent that provided U.S. market exclusivity for NuvaRing expired in April 2018 and generic competition began in December 2019. Accordingly, the Company is experiencing a rapid and substantial decline in U.S. NuvaRing sales and expects the decline to continue.

Biosimilars 

			Three Months Ended September 30,																		% Change Excluding Foreign Exchange						Nine Months Ended September 30,																		% Change Excluding Foreign Exchange
($ in millions)			2020						2019						% Change												2020						2019						% Change
Biosimilars			$	99					$	68					45		%				44		%				$	227					$	189					20		%				21		%

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Biosimilar products are marketed by the Company pursuant to an agreement with Samsung Bioepis Co., Ltd. (Samsung) to develop and commercialize multiple pre-specified biosimilar candidates. Currently, the Company markets Renflexis (infliximab-abda), a biosimilar to Remicade (infliximab) for the treatment of certain inflammatory diseases; Ontruzant (trastuzumab-dttb), a biosimilar to Herceptin (trastuzumab) for the treatment of human epidermal growth factor receptor 2 (HER2)-positive breast cancer and HER2 overexpressing gastric cancer; and Brenzys (etanercept biosimilar), a biosimilar to Enbrel for the treatment of certain inflammatory diseases. Merck’s commercialization territories under the agreement vary by product. Sales of biosimilars grew 45% and 20% in the third quarter and first nine months of 2020, respectively, primarily due to the launch of Ontruzant in Brazil in August 2020 and continued post-launch uptake of Renflexis in the United States and Canada. Sales growth in the first nine months of 2020 was partially offset by lower sales of Brenzys in Brazil.

In August 2020, the EC granted marketing authorization for Aybintio (bevacizumab) for the treatment of metastatic carcinoma of the colon or rectum, metastatic breast cancer, NSCLC, advanced and/or metastatic RCC, epithelial ovarian, fallopian tube and primary peritoneal cancer and cervical cancer. An application seeking approval of Aybintio in the United States was filed in September 2019.

Animal Health Segment

			Three Months Ended September 30,																		% Change Excluding Foreign Exchange						Nine Months Ended September 30,																		% Change Excluding Foreign Exchange
($ in millions)			2020						2019						% Change												2020						2019						% Change
Livestock			$	758					$	726					5		%				8		%				$	2,145					$	2,007					7		%				11		%
Companion Animal			462						396						17		%				18		%				1,390						1,264						10		%				12		%

Sales of livestock products grew 5% and 7% in the third quarter and first nine months of 2020, respectively, primarily driven by higher demand for ruminant, swine and poultry products. Sales growth in the first nine months of 2020 was also driven by the April 2019 acquisition of Antelliq Corporation (Antelliq) (see Note 2 to the condensed consolidated financial statements). Sales of companion animal products grew 17% in the third quarter of 2020 and 10% in the first nine months of 2020 primarily driven by higher demand for the Bravecto (fluralaner) line of products, as well as higher demand for companion animal vaccines.

Costs, Expenses and Other

			Three Months Ended September 30,																		Nine Months Ended September 30,
($ in millions)			2020						2019						% Change						2020						2019						% Change
Cost of sales			$	3,481					$	3,990					(13)		%				$	9,952					$	10,443					(5)		%
Selling, general and administrative			2,450						2,589						(5)		%				7,383						7,726						(4)		%
Research and development			3,390						3,204						6		%				7,721						7,324						5		%
Restructuring costs			114						232						(51)		%				269						444						(39)		%
Other (income) expense, net			(312)						35						*						(630)						362						*
			$	9,123					$	10,050					(9)		%				24,695						26,299						(6)		%

* Greater than 100%.

Cost of Sales

Cost of sales declined 13% and 5% in the third quarter and first nine months of 2020, respectively. Cost of sales includes the amortization of intangible assets recorded in connection with business acquisitions, which totaled $270 million and $320 million in the third quarter of 2020 and 2019, respectively, and $843 million and $1.1 billion in the first nine months of 2020 and 2019, respectively. Cost of sales also includes the amortization of amounts capitalized in connection with collaborations of $117 million and $81 million in the third quarter of 2020 and 2019, respectively, and $509 million and $307 million in the first nine months of 2020 and 2019, respectively. Additionally, costs include intangible asset impairment charges of $612 million and $693 million in the third quarter and first nine months of 2019, respectively, related to marketed products. The Company may recognize additional impairment charges in the future related to intangible assets that were measured at fair value and capitalized in connection with business acquisitions and such charges could be material. Also included in cost of sales are expenses associated with restructuring activities which amounted to $38 million and $62 million in the third quarter of 2020 and 2019, respectively, and $131 million and $161 million in the first nine months of 2020 and 2019, respectively, including accelerated depreciation and asset write-offs related to the planned sale or closure of manufacturing facilities. Separation costs associated with manufacturing-related headcount reductions have been incurred and are reflected in Restructuring costs as discussed below.

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Gross margin was 72.3% in the third quarter of 2020 compared with 67.8% in the third quarter of 2019. The gross margin improvement reflects lower intangible asset impairment charges (noted above), the favorable effect of product mix and lower restructuring costs, partially offset by the unfavorable effects of pricing pressure, inventory write-offs and foreign exchange. Gross margin was 71.9% in the first nine months of 2020 compared with 70.1% in the first nine months of 2019. The gross margin improvement was primarily driven by lower impairment charges and amortization related to intangible assets (noted above), as well as the favorable effect of product mix and lower restructuring costs, partially offset by the unfavorable effects of pricing pressure, royalties, manufacturing variances, and inventory write-offs.

Selling, General and Administrative

Selling, general and administrative (SG&A) expenses declined 5% and 4% in the third quarter and first nine months of 2020, respectively, primarily due to lower administrative and selling costs, including reduced travel and fewer meetings, due in part to the COVID-19 pandemic, and the favorable effect of foreign exchange, partially offset by costs related to the planned spin-off of Organon. Transaction costs related to the acquisition of ArQule also partially offset the decline in SG&A expenses in the first nine months of 2020 (see Note 2 to the condensed consolidated financial statements).

Research and Development

Research and development (R&D) expenses grew 6% and 5% in the third quarter and first nine months of 2020, respectively, primarily driven by higher upfront payments related to collaborations and license agreements (see Note 2 to the condensed consolidated financial statements), increased clinical development, discovery research and early drug development spending, as well as higher restructuring costs, partially offset by a charge in 2019 for the acquisition of Peloton Therapeutics, Inc. (Peloton) (see Note 2 to the condensed consolidated financial statements), lower costs associated with the COVID-19 pandemic (net of spending on COVID-19-related vaccine and antiviral research programs), and the favorable effect of foreign exchange.

R&D expenses are comprised of the costs directly incurred by MRL, the Company’s research and development division that focuses on human health-related activities, which were $1.6 billion in both the third quarter of 2020 and 2019, and $4.7 billion and $4.4 billion in the first nine months of 2020 and 2019, respectively. Also included in R&D expenses are Animal Health research costs, licensing costs and costs incurred by other divisions in support of R&D activities, including depreciation, production and general and administrative, which in the aggregate were approximately $645 million and $655 million for the third quarter of 2020 and 2019, respectively, and were $1.9 billion in both the first nine months of 2020 and 2019. In addition, R&D expenses include expense or income related to changes in the estimated fair value measurement of liabilities for contingent consideration recorded in connection with business acquisitions. The Company recorded a net reduction in expenses of $48 million and $36 million in the first nine months of 2020 and 2019, respectively, related to the changes in these estimates. R&D expenses also reflect $19 million and $67 million of accelerated depreciation costs in connection with restructuring activities in the third quarter and first nine months of 2020, respectively.

Restructuring Costs

In early 2019, Merck approved a new global restructuring program (Restructuring Program) as part of a worldwide initiative focused on further optimizing the Company’s manufacturing and supply network, as well as reducing its global real estate footprint. This program is a continuation of the Company’s plant rationalization, builds on prior restructuring programs and does not include any actions associated with the planned spin-off of Organon. As the Company continues to evaluate its global footprint and overall operating model, it subsequently identified additional actions under the Restructuring Program, and could identify further actions over time. The actions currently contemplated under the Restructuring Program are expected to be substantially completed by the end of 2023, with the cumulative pretax costs to be incurred by the Company to implement the program estimated to be approximately $2.5 billion. The Company expects to record charges of approximately $800 million in 2020 related to the Restructuring Program. The Company anticipates the actions under the Restructuring Program to result in annual net cost savings of approximately $900 million by the end of 2023. Actions under previous global restructuring programs have been substantially completed.

Restructuring costs, primarily representing separation and other related costs associated with these restructuring activities, were $114 million and $232 million for the third quarter of 2020 and 2019, respectively, and $269 million and $444 million in the first nine months of 2020 and 2019, respectively. Separation costs incurred were associated with actual headcount reductions, as well as estimated expenses under existing severance programs for headcount reductions that were probable and could be reasonably estimated. Also included in restructuring costs are asset abandonment, facility shut-down and other related costs, as well as employee-related costs such as curtailment, settlement and termination charges associated with pension and other postretirement benefit plans and share-based compensation plan costs. For segment reporting, restructuring costs are unallocated expenses.

Additional costs associated with the Company’s restructuring activities are included in Cost of sales, Selling, general and administrative expenses and Research and development costs. The Company recorded aggregate pretax costs of

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$186 million and $296 million in the third quarter of 2020 and 2019, respectively, and $504 million and $642 million in the first nine months of 2020 and 2019, respectively, related to restructuring program activities (see Note 4 to the condensed consolidated financial statements).

Other (Income) Expense, Net

For details on the components of Other (income) expense, net see Note 13 to the condensed consolidated financial statements.

Segment Profits
			Three Months Ended September 30,												Nine Months Ended September 30,
($ in millions)			2020						2019						2020						2019
Pharmaceutical segment profits			$	7,974					$	7,747					$	22,010					$	21,437
Animal Health segment profits			451						423						1,336						1,243
Other non-reportable segment profits			(1)						(2)						1						(2)
Other			(4,996)						(5,821)						(12,563)						(14,005)
Income before taxes			$	3,428					$	2,347					$	10,784					$	8,673

Pharmaceutical segment profits are comprised of segment sales less standard costs, as well as SG&A expenses directly incurred by the segment. Animal Health segment profits are comprised of segment sales, less all cost of sales, as well as SG&A expenses and research and development costs directly incurred by the segment. For internal management reporting presented to the chief operating decision maker, Merck does not allocate the remaining cost of sales not included in segment profits as described above, research and development expenses incurred by MRL, or general and administrative expenses, nor the cost of financing these activities. Separate divisions maintain responsibility for monitoring and managing these costs, including depreciation related to fixed assets utilized by these divisions and, therefore, they are not included in segment profits. Also excluded from the determination of segment profits are costs related to restructuring activities and acquisition and divestiture-related costs, including the amortization of purchase accounting adjustments, intangible asset impairment charges, and changes in the estimated fair value measurement of liabilities for contingent consideration. Additionally, segment profits do not reflect other expenses from corporate and manufacturing cost centers and other miscellaneous income or expense. These unallocated items are reflected in “Other” in the above table. Also included in “Other” are miscellaneous corporate profits (losses), as well as operating profits (losses) related to third-party manufacturing sales.

Pharmaceutical segment profits grew 3% in both the third quarter and first nine months of 2020 driven primarily by higher sales, as well as lower administrative and selling costs. Animal Health segment profits grew 6% and 7% in the third quarter and first nine months of 2020, respectively, reflecting higher sales and lower promotional costs, partially offset by higher R&D costs and the unfavorable effect of foreign exchange.

Taxes on Income

The effective income tax rates of 14.1% and 18.7% for the third quarter of 2020 and 2019, respectively, and 14.9% and 14.5% for the first nine months of 2020 and 2019, respectively, reflect the impacts of acquisition and divestiture-related costs and restructuring costs, partially offset by the beneficial impact of foreign earnings. The effective income tax rates in the third quarter and first nine months of 2019 also reflect the unfavorable impact of a charge for the acquisition of Peloton for which no tax benefit was recognized and the favorable impact of product mix on the estimated 2019 full-year tax rate. In addition, the effective income tax rate for the first nine months of 2019 reflects the favorable impact of a $360 million net tax benefit related to the settlement of certain federal income tax matters.

In the first quarter of 2019, the Internal Revenue Service (IRS) concluded its examinations of Merck’s 2012-2014 U.S. federal income tax returns. As a result, the Company was required to make a payment of $107 million. The Company’s reserves for unrecognized tax benefits for the years under examination exceeded the adjustments relating to this examination period and therefore the Company recorded a $360 million net tax benefit in the first nine months of 2019. This net benefit reflects reductions in reserves for unrecognized tax benefits for tax positions relating to the years that were under examination, partially offset by additional reserves for tax positions not previously reserved for.

Net Loss Attributable to Noncontrolling Interests

Net loss attributable to noncontrolling interests of $73 million for the first nine months of 2019 includes the portion of goodwill impairment charges related to certain businesses in the Healthcare Services segment that are attributable to noncontrolling interests.

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Net Income and Earnings per Common Share

Net income attributable to Merck & Co., Inc. was $2.9 billion for the third quarter of 2020 compared with $1.9 billion for the third quarter of 2019 and was $9.2 billion for the first nine months of 2020 compared with $7.5 billion for the first nine months of 2019. Earnings per common share assuming dilution attributable to Merck & Co., Inc. common shareholders (EPS) for the third quarter of 2020 were $1.16 compared with $0.74 in the third quarter of 2019 and were $3.61 for the first nine months of 2020 compared with $2.89 for the first nine months of 2019.

Non-GAAP Income and Non-GAAP EPS

Non-GAAP income and non-GAAP EPS are alternative views of the Company’s performance that Merck is providing because management believes this information enhances investors’ understanding of the Company’s results as it permits investors to understand how management assesses performance. Non-GAAP income and non-GAAP EPS exclude certain items because of the nature of these items and the impact that they have on the analysis of underlying business performance and trends. The excluded items (which should not be considered non-recurring) consist of acquisition and divestiture-related costs, restructuring costs and certain other items. These excluded items are significant components in understanding and assessing financial performance. Non-GAAP income and non-GAAP EPS are important internal measures for the Company. Senior management receives a monthly analysis of operating results that includes non-GAAP EPS. Management uses these measures internally for planning and forecasting purposes and to measure the performance of the Company along with other metrics. In addition, senior management’s annual compensation is derived in part using non-GAAP pretax income. Since non-GAAP income and non-GAAP EPS are not measures determined in accordance with GAAP, they have no standardized meaning prescribed by GAAP and, therefore, may not be comparable to the calculation of similar measures of other companies. The information on non-GAAP income and non-GAAP EPS should be considered in addition to, but not as a substitute for or superior to, net income and EPS prepared in accordance with generally accepted accounting principles in the United States (GAAP).

A reconciliation between GAAP financial measures and non-GAAP financial measures is as follows:

			Three Months Ended September 30,												Nine Months Ended September 30,
($ in millions except per share amounts)			2020						2019						2020						2019
Income before taxes as reported under GAAP			$	3,428					$	2,347					$	10,784					$	8,673
Increase (decrease) for excluded items:
Acquisition and divestiture-related costs			508						975						1,551						2,183
Restructuring costs			186						296						504						642
Other items:
Charges for collaborations and acquisitions (1)			1,082						982						1,082						982
Other			(1)						—						(17)						48
Non-GAAP income before taxes			5,203						4,600						13,904						12,528
Taxes on income as reported under GAAP			483						440						1,611						1,259
Estimated tax benefit on excluded items (2)			356						281						616						555
Adjustment to tax benefits recorded in conjunction with the 2015 Cubist Pharmaceuticals, Inc. acquisition			(67)						—						(67)						—
Net tax benefit from the settlement of certain federal income tax matters			—						—						—						360
Tax charge related to finalization of treasury regulations for the Tax Cuts and Job Act of 2017			—						—						—						(67)
Non-GAAP taxes on income			772						721						2,160						2,107
Non-GAAP net income			4,431						3,879						11,744						10,421
Less: Net income (loss) attributable to noncontrolling interests as reported under GAAP			4						6						12						(73)
Acquisition and divestiture-related costs attributable to noncontrolling interests			—						—						—						89
Non-GAAP net income attributable to noncontrolling interests			4						6						12						16
Non-GAAP net income attributable to Merck & Co., Inc.			$	4,427					$	3,873					$	11,732					$	10,405
EPS assuming dilution as reported under GAAP			$	1.16					$	0.74					$	3.61					$	2.89
EPS difference			0.58						0.77						1.01						1.13
Non-GAAP EPS assuming dilution			$	1.74					$	1.51					$	4.62					$	4.02

(1)    Amount in 2020 includes $832 million related to transactions with Seagen. Amount in 2019 represents a charge for the acquisition of Peloton. See Note 2 to the condensed consolidated financial statements.

(2) The estimated tax impact on the excluded items is determined by applying the statutory rate of the originating territory of the non-GAAP adjustments.

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Acquisition and Divestiture-Related Costs

Non-GAAP income and non-GAAP EPS exclude the impact of certain amounts recorded in connection with business acquisitions and divestitures. These amounts include the amortization of intangible assets and amortization of purchase accounting adjustments to inventories, as well as intangible asset impairment charges, and expense or income related to changes in the estimated fair value measurement of liabilities for contingent consideration. Also excluded are integration, transaction, and certain other costs associated with business acquisitions and divestitures.

Restructuring Costs

Non-GAAP income and non-GAAP EPS exclude costs related to restructuring actions (see Note 4 to the condensed consolidated financial statements). These amounts include employee separation costs and accelerated depreciation associated with facilities to be closed or divested. Accelerated depreciation costs represent the difference between the depreciation expense to be recognized over the revised useful life of the asset, based upon the anticipated date the site will be closed or divested or the equipment disposed of, and depreciation expense as determined utilizing the useful life prior to the restructuring actions. Restructuring costs also include asset abandonment, facility shut-down and other related costs, as well as employee-related costs such as curtailment, settlement and termination charges associated with pension and other postretirement benefit plans and share-based compensation costs.

Certain Other Items

Non-GAAP income and non-GAAP EPS exclude certain other items. These items are adjusted for after evaluating them on an individual basis, considering their quantitative and qualitative aspects. Typically, these consist of items that are unusual in nature, significant to the results of a particular period or not indicative of future operating results. Excluded from non-GAAP income and non-GAAP EPS in 2020 are upfront payments related to licensing arrangements and collaborations, including the transactions with Seagen (see Note 2 to the condensed consolidated financial statements), and an adjustment to tax benefits recorded in conjunction with the 2015 Cubist Pharmaceuticals, Inc. acquisition. Excluded from non-GAAP income and non-GAAP EPS in 2019 is a charge for the acquisition of Peloton (see Note 2 to the condensed consolidated financial statements), a net tax benefit related to the settlement of certain federal income tax matters (see Note 14 to the condensed consolidated financial statements) and a tax charge related to the finalization of U.S. treasury regulations related to the Tax Cuts and Jobs Act of 2017.

Research and Development Update

In July 2020, the FDA accepted for priority review the NDA for vericiguat, an orally administered sGC stimulator, to reduce the risk of cardiovascular death and heart failure hospitalization following a worsening heart failure event in patients with symptomatic chronic heart failure with reduced ejection fraction, in combination with other heart failure therapies. The FDA set a Prescription Drug User Fee Act (PDUFA), or target action, date of January 20, 2021. Vericiguat is being jointly developed with Bayer (see Note 3 to the condensed consolidated financial statements). The application is based on results from the Phase 3 VICTORIA trial, which is the first contemporary outcomes study focused exclusively on a population with worsening chronic heart failure who are at high risk for cardiovascular mortality and repeated heart failure hospitalizations. Data from VICTORIA were presented at the virtual American College of Cardiology’s 69th Annual Scientific Session together with World Congress of Cardiology and published in The New England Journal of Medicine. Vericiguat is also under review in the EU and in Japan. Merck and Bayer plan to share VICTORIA data with regulatory authorities worldwide.

Koselugo is under review in the EU for the treatment of pediatric patients two years of age and older with NF1 who have symptomatic, inoperable PN based on positive results from the NCI CTEP-sponsored Phase 2 SPRINT Stratum 1 trial. Koselugo was approved by the FDA in April 2020. Koselugo is being jointly developed and commercialized with AstraZeneca globally (see Note 3 to the condensed consolidated financial statements).

Keytruda is an anti-PD-1 therapy approved for the treatment of many cancers that is in clinical development for expanded indications. These approvals were the result of a broad clinical development program that currently consists of more than 1,300 clinical trials, including more than 900 trials that combine Keytruda with other cancer treatments. These studies encompass more than 30 cancer types including: biliary tract, cervical, colorectal, cutaneous squamous cell, endometrial, esophageal, gastric, glioblastoma, head and neck, hepatocellular, Hodgkin lymphoma, non-Hodgkin lymphoma, melanoma, mesothelioma, nasopharyngeal, non-small-cell lung, ovarian, prostate, renal, small-cell lung, triple-negative breast and urothelial, many of which are currently in Phase 3 clinical development. Further trials are being planned for other cancers.

In July 2020, the FDA accepted and granted Priority Review for a supplemental Biologics License Application (BLA) seeking accelerated approval for Keytruda in combination with chemotherapy for the treatment of patients with locally recurrent unresectable or metastatic triple-negative breast cancer (TNBC) whose tumors express PD-L1 (CPS ≥10). The application was based on data from the KEYNOTE-355 trial in which Keytruda plus chemotherapy demonstrated a statistically significant and clinically meaningful improvement in progression-free survival (PFS) compared with chemotherapy alone in patients whose tumors expressed PD-L1 at CPS ≥10. In patients whose tumors expressed PD-L1 with

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CPS ≥1, Keytruda plus chemotherapy improved PFS versus chemotherapy alone, however these results did not meet statistical significance. These data were presented at the virtual scientific program of the 2020 American Society of Clinical Oncology (ASCO) Annual Meeting. As previously announced, the trial will continue without changes to evaluate the other dual primary endpoint of overall survival (OS). The FDA set a PDUFA date of November 28, 2020. In October 2020, Merck announced the submission of KEYNOTE-355 to the Japan PMDA.

Also in July 2020, the FDA accepted for standard review a supplemental BLA for Keytruda for the treatment of patients with high-risk, early-stage TNBC, in combination with chemotherapy as neoadjuvant treatment, and then as a single agent as adjuvant treatment after surgery. The application was based on data from the KEYNOTE-522 trial in which neoadjuvant Keytruda plus chemotherapy resulted in a statistically significant increase in pathologic complete response in patients with early-stage TNBC, regardless of PD-L1 expression. The Keytruda regimen also demonstrated a favorable trend for the other dual primary endpoint of event-free survival. An interim analysis for this study was conducted by the Independent Data Monitoring Committee (DMC). Based on the recommendation of the DMC, the study continues to evaluate event-free survival. Data from the KEYNOTE-522 trial were presented at the European Society for Medical Oncology 2019 Congress. As previously announced, Keytruda plus chemotherapy was granted Breakthrough Therapy designation by the FDA in September 2019 for the neoadjuvant treatment of patients with high-risk, early-stage TNBC. The PDUFA date for this application is March 29, 2021.

The Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency (EMA) announced the start of a procedure to extend the currently approved therapeutic indication for the treatment of relapsed or refractory cHL in adults to an earlier line of therapy based on the pivotal Phase 3 KEYNOTE-204 trial, in which Keytruda demonstrated a significant improvement in PFS compared to brentuximab vedotin (BV), a current standard of care in this patient population. Data from KEYNOTE-204 were presented during the virtual scientific program of the 2020 ASCO Annual Meeting. Keytruda was approved for this indication by the FDA in October 2020. The procedure also seeks to extend the indication to include pediatric patients.

Keytruda is also under review in the EU and in Japan for the first-line treatment of patients with MSI-H or mismatch repair deficient unresectable or metastatic colorectal cancer based on the results from the Phase 3 KEYNOTE-177 trial. Keytruda was approved for this indication by the FDA in June 2020.

In addition to the Breakthrough Therapy designation from the FDA for the combination of Keytruda with neoadjuvant chemotherapy for the treatment of high-risk, early-stage TNBC noted above, Keytruda also received Breakthrough Therapy designation from the FDA in February 2020 for the combination of Keytruda with PADCEV (enfortumab vedotin-ejfv), in the first-line setting for the treatment of patients with unresectable locally advanced or metastatic urothelial cancer who are not eligible for cisplatin-containing chemotherapy. The FDA’s Breakthrough Therapy designation is intended to expedite the development and review of a candidate that is planned for use, alone or in combination, to treat a serious or life-threatening disease or condition when preliminary clinical evidence indicates that the drug may demonstrate substantial improvement over existing therapies on one or more clinically significant endpoints.

In August 2020, Merck announced first-time data from the pivotal Phase 3 KEYNOTE-590 trial evaluating Keytruda in combination with platinum-based chemotherapy for the first-line treatment of patients with locally advanced or metastatic esophageal and gastroesophageal junction cancer. In the study, Keytruda in combination with chemotherapy significantly improved OS and PFS versus chemotherapy in all randomized patients; it was demonstrated that the risk of death was reduced by 27% versus chemotherapy as first-line treatment for locally advanced or metastatic esophageal cancer. With these results, Keytruda is the first anti-PD-1 therapy in combination with chemotherapy to show superior OS, PFS and objective response rate (ORR) versus chemotherapy, the current standard of care, for these patients regardless of histology or PD-L1 expression status. These data were presented at the European Society for Medical Oncology (ESMO) Virtual Congress 2020. Merck will be sharing these data with regulatory authorities worldwide.

In June 2020, Merck announced that the Phase 3 KEYNOTE-361 trial evaluating Keytruda in combination with chemotherapy for the first-line treatment of patients with advanced or metastatic urothelial carcinoma (bladder cancer) did not meet its pre-specified dual primary endpoints of OS or PFS, compared with standard of care chemotherapy. In the final analysis of the study, there was an improvement in OS and PFS for patients treated with Keytruda in combination with chemotherapy compared to chemotherapy alone; however, these results did not meet statistical significance per the pre-specified statistical plan. The monotherapy arm of the study was not formally tested, since superiority was not reached for OS or PFS in the Keytruda combination arm. Keytruda has three FDA-approved bladder cancer indications across multiple stages of bladder cancer. Additionally, Merck has an extensive clinical development program in bladder cancer and is continuing to evaluate Keytruda as monotherapy and in combination with other anti-cancer therapies across several disease settings (i.e., metastatic, muscle invasive bladder cancer, and non-muscle invasive bladder cancer).

In May 2020, Merck announced positive results from two studies from the Company’s lung cancer research program. Initial results from the Phase 2 KEYNOTE-799 trial evaluating Keytruda plus concurrent chemoradiation therapy

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demonstrated an ORR of 67.0% in Cohort A (squamous and nonsquamous NSCLC patients who received paclitaxel plus carboplatin) and 56.6% in Cohort B (nonsquamous NSCLC patients who received cisplatin plus pemetrexed) in untreated patients with unresectable, locally advanced stage III NSCLC.

Additionally in May 2020, Merck and Eisai presented data from analyses of two trials evaluating Keytruda plus Lenvima at the 2020 ASCO Annual Meeting, in which the Keytruda plus Lenvima combination demonstrated clinically meaningful ORR: the KEYNOTE-524/Study 116 trial in patients with unresectable HCC with no prior systemic therapy and the KEYNOTE-146/Study 111 trial in patients with metastatic clear cell renal cell carcinoma (ccRCC) who progressed following immune checkpoint inhibitor therapy.

In July 2020, Merck and Eisai announced that the FDA issued a Complete Response Letter (CRL) regarding Merck’s and Eisai’s applications seeking accelerated approval of Keytruda plus Lenvima for the first-line treatment of patients with unresectable HCC based on data from the Phase 1b KEYNOTE-524/Study 116 trial, which showed clinically meaningful efficacy in the single-arm setting. These data supported a Breakthrough Therapy designation granted by the FDA in July 2019. Ahead of the PDUFA action dates of Merck’s and Eisai’s applications, another combination therapy was approved based on a randomized, controlled trial that demonstrated improvement in OS versus standard-of-care treatment. Consequently, the CRL stated that Merck’s and Eisai’s applications do not provide evidence that Keytruda in combination with Lenvima represents a meaningful advantage over available therapies for the treatment of unresectable or metastatic HCC with no prior systemic therapy for advanced disease. Since the applications for KEYNOTE-524/Study 116 no longer meet the criteria for accelerated approval, both companies plan to work with the FDA to take appropriate next steps, which include conducting a well-controlled clinical trial that demonstrates substantial evidence of effectiveness and the clinical benefit of the combination. As such, LEAP-002, the Phase 3 trial evaluating the Keytruda plus Lenvima combination as a first-line treatment for advanced HCC, is currently underway and fully enrolled. The CRL does not impact the current approved indications for Keytruda or for Lenvima.

In July 2020, the FDA granted Breakthrough Therapy designation to the hypoxia-inducible factor-2 alpha (HIF-2α) inhibitor MK-6482, a novel investigational candidate for the treatment of patients with von Hippel-Lindau (VHL) disease-associated RCC with nonmetastatic RCC tumors less than three centimeters in size, unless immediate surgery is required. The FDA also granted orphan drug designation to MK-6482 for VHL disease. These designations are based on data from a Phase 2 trial evaluating MK-6482 in patients with VHL-associated ccRCC, which were presented at the 2020 ASCO Annual Meeting. Additionally, Phase 2 data showing anti-tumor responses in VHL disease patients with ccRCC and other tumors were presented at the ESMO Virtual Congress 2020.

In September 2020, Merck and Seagen announced a collaboration to globally develop and commercialize Seagen’s ladiratuzumab vedotin (MK-6440), an investigational antibody-drug conjugate targeting LIV-1, which is currently in Phase 2 clinical trials for breast cancer and other solid tumors. The collaboration will pursue a broad joint development program evaluating ladiratuzumab vedotin as monotherapy and in combination with Keytruda in triple-negative breast cancer, hormone receptor-positive breast cancer and other LIV-1-expressing solid tumors. Seagen also granted Merck an exclusive license and entered into a co-development agreement with Merck to accelerate the global reach of Tukysa (MK-7119), a small molecule tyrosine kinase inhibitor, for the treatment of HER2-positive cancers, in Asia, the Middle East and Latin America and other regions outside of the United States, Canada and Europe. See Note 2 to the condensed consolidated financial statements.

Lynparza is an oral PARP inhibitor currently approved for certain types of advanced ovarian, breast, pancreatic and prostate cancers being co-developed for multiple cancer types as part of a collaboration with AstraZeneca (see Note 3 to the condensed consolidated financial statements).

In May 2020, the results from the Phase 3 GY004 trial, led by NRG Oncology and sponsored by the U.S. NCI, were presented at the 2020 ASCO Annual Meeting. This follows the March 2020, Merck and AstraZeneca announcement of the high-level results from the Phase 3 GY004 trial that examined primarily the efficacy and safety of investigational medicine cediranib in combination with Lynparza versus platinum-based chemotherapy in patients with platinum-sensitive relapsed ovarian cancer. The trial did not meet the primary endpoint in the intent-to-treat population of a statistically significant improvement in PFS with cediranib in combination with Lynparza vs. platinum-based chemotherapy.

In September 2020, Merck announced the results from two ongoing pivotal Phase 3 trials (COUGH-1 and COUGH-2) evaluating the efficacy and safety of gefapixant (MK-7264), an investigational, orally administered, selective P2X3 receptor antagonist, for the treatment of refractory or unexplained chronic cough. In these studies, adult patients treated with gefapixant 45 mg twice daily demonstrated a statistically significant reduction in 24-hour cough frequency versus placebo at 12 weeks (COUGH-1) and 24 weeks (COUGH-2). The gefapixant 15 mg twice daily treatment arms did not meet the primary efficacy endpoint in either Phase 3 study. These results were presented at the Virtual European Respiratory Society International Congress 2020. Merck plans to share data from COUGH-1 and COUGH-2 with regulatory authorities worldwide.

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In October 2020, Merck announced Week 96 data from the Phase 2b trial (NCT03272347) evaluating the efficacy and safety of islatravir, the company’s investigational oral nucleoside reverse transcriptase translocation inhibitor (NRTTI), in combination with doravirine (Pifeltro), in treatment-naïve adults with HIV-1 infection. Week 96 findings demonstrated that the combination of islatravir and doravirine maintained virologic suppression (as measured by the number of study participants achieving HIV-1 RNA levels <50 copies/mL, similar to Delstrigo (doravirine/lamivudine/tenofovir disoproxil fumarate)), and the findings were consistent with Week 48 results. Additional Week 96 data from the study show low rates of participants meeting the definition of protocol-defined virologic failure in both the islatravir plus doravirine and the Delstrigo treatment arms, and no participants in either arm met the criteria for resistance testing. These data were presented at the virtual 2020 International Congress on Drug Therapy in HIV Infection (HIV Glasglow).

In October 2020, Merck announced findings from two Phase 3 studies evaluating the safety, tolerability and immunogenicity of V114, the Company’s investigational 15-valent pneumococcal conjugate vaccine. In the PNEU-PATH (V114-016) study, healthy adults 50 years of age and older received V114 or PCV13 followed by Pneumovax 23 one year later. Immune responses following vaccination with Pneumovax 23 were comparable in both vaccination groups for the 15 serotypes in V114. Results also showed that at 30 days post vaccination with either V114 or PCV13, immune responses were comparable for both groups across the 13 serotypes shared by the conjugate vaccines and higher in the V114 group for serotypes 22F and 33F, the two serotypes not included in PCV13. In PNEU-DAY (V114-017), a Phase 3 study in immunocompetent adults 18 to 49 years of age with underlying medical conditions associated with increased risk for pneumococcal disease, V114 generated immune responses generally comparable to PCV13 for the 13 shared serotypes and higher immune responses for serotypes 22F and 33F at 30 days post-vaccination.

In September 2020, Merck announced that two Phase 3 studies evaluating the safety, tolerability and immunogenicity of V114 met their primary immunogenicity objectives. The pivotal PNEU-AGE (V114-019) study in healthy adults 50 years of age or older demonstrated that V114 is non-inferior to the currently available 13-valent pneumococcal conjugate vaccine (PCV13) for the 13 serotypes targeted by both vaccines and superior for serotypes 22F and 33F, the two serotypes targeted by V114 but not PCV13. The PNEU-AGE study also met the key secondary immunogenicity objective, demonstrating superiority of V114 compared to PCV13 for serotype 3, a leading cause of invasive pneumococcal disease globally. In another Phase 3 study, PNEU-TRUE (V114-020), in healthy adults 50 years of age or older, V114 met its primary immunogenicity objective demonstrating equivalent immune response across all 15 serotypes for three different lots of V114.

In June 2020, Merck announced results from two initial Phase 3 studies evaluating the safety, tolerability and immunogenicity of V114. Results from the PNEU-WAY (V114-018) study in adults 18 years of age or older living with HIV showed that V114 elicited an immune response to all 15 serotypes included in the vaccine, including serotypes 22F and 33F. Results from the PNEU-FLU (V114-021) study in healthy adults 50 years of age or older showed that V114 can be given concomitantly with the quadrivalent influenza vaccine. These data were announced and published in the International Symposium on Pneumococci and Pneumococcal Diseases digital library in lieu of an in-person meeting.

The V114 Phase 3 clinical development program is comprised of 16 trials investigating the safety, tolerability and immunogenicity of V114 in a variety of populations who are at increased risk for pneumococcal disease including both healthy older adult and healthy pediatric populations, as well as people who are immunocompromised or have certain chronic conditions. Findings from the V114 Phase 3 clinical program, including the studies above, will be presented at a future scientific congress and will form the basis for global regulatory licensure applications, beginning with the FDA before the end of the year.

In June 2020, Merck and Pfizer Inc. announced the presentation of results from the Phase 3 VERTIS CV cardiovascular (CV) outcomes trial that evaluated Steglatro (ertugliflozin), an oral sodium-glucose cotransporter 2 (SGLT2) inhibitor, versus placebo, added to background standard of care treatment, in patients with type 2 diabetes and atherosclerotic CV disease. The study met the primary endpoint of non-inferiority on major adverse CV events (MACE), which is a composite of CV death, nonfatal myocardial infarction or nonfatal stroke, compared to placebo. The key secondary endpoints of superiority for Steglatro versus placebo for time to the first occurrence of the composite of CV death or hospitalization for heart failure, time to CV death alone and time to the first occurrence of the composite of renal death, dialysis/transplant or doubling of serum creatinine from baseline were not met. While not a pre-specified hypothesis for statistical testing, a reduction in hospitalization for heart failure was observed with Steglatro.

In July 2020, the FDA granted V181, the Company’s investigational dengue vaccine in Phase 1 development, Fast Track designation.

The chart below reflects the Company’s research pipeline as of November 2, 2020. Candidates shown in Phase 3 include specific products and the date such candidate entered into Phase 3 development. Candidates shown in Phase 2 include the most advanced compound with a specific mechanism or, if listed compounds have the same mechanism, they are each currently intended for commercialization in a given therapeutic area. Small molecules and biologics are given MK-number designations and vaccine candidates are given V-number designations. Except as otherwise noted, candidates in Phase 1,

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additional indications in the same therapeutic area (other than with respect to cancer) and additional claims, line extensions or formulations for in-line products are not shown.

Phase 2			Phase 3 (Phase 3 entry date)			Under Review
Antiviral COVID-19 MK-4482 (molnupiravir)(1) Cancer MK-1026      Hematological Malignancies MK-1308 (quavonlimab)(2) Melanoma Non-Small-Cell Lung MK-1454(2) Head and Neck MK-3475 Keytruda Advanced Solid Tumors MK-4280(2)      Hematological Malignancies      Non-Small-Cell Lung MK-5890(2)      Non-Small-Cell Lung MK-6440 (ladiratuzumab vedotin)(1)(3) Advanced Solid Tumors Breast MK-7119 Tukysa(1) Colorectal MK-7339 Lynparza(1)(3) Advanced Solid Tumors MK-7684 (vibostolimab)(2)     Melanoma Non-Small-Cell Lung MK-7902 Lenvima(1)(2) Advanced Solid Tumors Biliary Tract Colorectal Gastric Glioblastoma V937 Breast Cutaneous Squamous Cell Melanoma Head and Neck Chikungunya virus V184 Cytomegalovirus V160 HIV-1 Prevention MK-8591 (islatravir) Overgrowth Syndrome MK-7075 (miransertib) Pneumococcal Vaccine Adult V116 Respiratory Syncytial Virus MK-1654 Schizophrenia MK-8189			Cancer MK-3475 Keytruda Biliary Tract (September 2019) Breast (October 2015) (EU) Cervical (October 2018) (EU) Cutaneous Squamous Cell (August 2019) (EU) Endometrial (August 2019) (EU) Esophageal (December 2015) (EU) Gastric (May 2015) (EU) Hepatocellular (May 2016) (EU) Mesothelioma (May 2018) Nasopharyngeal (April 2016) Ovarian (December 2018) Prostate (May 2019) Small-Cell Lung (May 2017) (EU) MK-6482 Renal Cell (February 2020) MK-7119 Tukysa(1) Breast (October 2019) MK-7339 Lynparza(1)(2) Colorectal (August 2020) Non-Small-Cell Lung (June 2019) MK-7902 Lenvima(1)(2) Bladder (May 2019) Endometrial (June 2018) (EU) Head and Neck (February 2020) Melanoma (March 2019) Non-Small-Cell Lung (March 2019) Cough MK-7264 (gefapixant) (March 2018) HIV-1 Infection      MK-8591A (doravirine/islatravir) (February 2020) Pneumoconjugate Vaccine V114 (June 2018)			New Molecular Entities/Vaccines Heart Failure MK-1242 (vericiguat)(1) (U.S.) (EU) (JPN) Pediatric Neurofibromatosis Type 1 MK-5618 (selumetinib)(1) (EU) Certain Supplemental Filings Cancer MK-3475 Keytruda • Metastatic Triple-Negative Breast Cancer          (KEYNOTE-355) (U.S.) (JPN) • Early-Stage Triple-Negative Breast Cancer          (KEYNOTE-522) (U.S.) • Refractory Classical Hodgkin Lymphoma          (KEYNOTE-204) (EU) • Unresectable or Metastatic MSI-H or dMMR Colorectal          Cancer (KEYNOTE-177) (EU) (JPN) MK-7902 Lenvima(1) • First-Line Metastatic Hepatocellular Carcinoma          (KEYNOTE-524) (U.S.)(2)(4) • Thymic Carcinoma (NCCH1508/REMORA) (JPN)
						Footnotes: (1) Being developed in a collaboration (2) Being developed in combination with Keytruda. (3) Being developed as monotherapy and in combination with Keytruda. (4) In July 2020, the FDA issued a CRL for Merck’s and Eisai’s applications. Merck and Eisai are reviewing the letter and will submit data to the FDA.

Liquidity and Capital Resources

($ in millions)			September 30, 2020						December 31, 2019
Cash and investments			$	8,728					$	11,919
Working capital			6,172						5,263
Total debt to total liabilities and equity			32.0		%				31.2		%

Cash provided by operating activities was $6.2 billion in the first nine months of 2020 compared with $8.6 billion in the first nine months of 2019. Cash provided by operating activities in the first nine months of 2020 includes $2.1 billion of payments related to collaborations compared with $505 million in the first nine months of 2019. Cash provided by operating activities continues to be the Company’s primary source of funds to finance operating needs, capital expenditures, treasury stock purchases and dividends paid to shareholders.

Cash used in investing activities was $4.7 billion in the first nine months of 2020 compared with $1.9 billion in the first nine months of 2019. The increase was driven primarily by lower proceeds from sales of securities and other investments and higher capital expenditures, partially offset by lower purchases of securities and other investments and lower use of cash for acquisitions.

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Cash used in financing activities was $4.2 billion in the first nine months of 2020 compared with $6.9 billion in the first nine months of 2019. The lower use of cash in financing activities was driven primarily by a net increase in short-term borrowings in 2020 compared with a net decrease in short-term borrowing in 2019, as well as lower purchases of treasury stock, partially offset by higher payments on debt (see below), lower proceeds from the issuance of debt (see below), higher dividends paid to shareholders, and lower proceeds from the exercise of stock options.

Capital expenditures totaled $3.2 billion and $2.3 billion for the first nine months of 2020 and 2019, respectively. The increased capital expenditures reflect investment in new capital projects focused primarily on increasing manufacturing capacity for Merck’s key products, as well as the purchase of a manufacturing facility in Dunboyne, Ireland to support upcoming product launches (see Note 2 to the condensed consolidated financial statements).

The Company has accounts receivable factoring agreements with financial institutions in certain countries to sell accounts receivable. The Company factored $2.1 billion and $2.7 billion of accounts receivable in the third quarter of 2020 and the fourth quarter of 2019, respectively, under these factoring arrangements, which reduced outstanding accounts receivable. The cash received from the financial institutions is reported within operating activities in the Condensed Consolidated Statement of Cash Flows. In certain of these factoring arrangements, for ease of administration, the Company will collect customer payments related to the factored receivables, which it then remits to the financial institutions. The net cash flows relating to these collections are reported as financing activities in the Condensed Consolidated Statement of Cash Flows.

Dividends paid to stockholders were $4.7 billion and $4.3 billion for the first nine months of 2020 and 2019, respectively. In May 2020, the Board of Directors declared a quarterly dividend of $0.61 per share on the Company’s common stock for the third quarter that was paid in July 2020. In July 2020, the Board of Directors declared a quarterly dividend of $0.61 per share on the Company’s common stock for the fourth quarter that was paid in October 2020.

In February 2020, the Company’s $1.25 billion, 1.85% notes and $700 million floating-rate notes matured in accordance with their terms and were repaid.

In June 2020, the Company issued $4.5 billion principal amount of senior unsecured notes consisting of $1.0 billion of 0.75% notes due 2026, $1.25 billion of 1.45% notes due 2030, $1.0 billion of 2.35% notes due 2040 and $1.25 billion of 2.45% notes due 2050. Merck used the net proceeds from the offering for general corporate purposes, including without limitation the repayment of outstanding commercial paper borrowings and other indebtedness with upcoming maturities.

In March 2019, the Company issued $5.0 billion principal amount of senior unsecured notes consisting of $750 million of 2.90% notes due 2024, $1.75 billion of 3.40% notes due 2029, $1.0 billion of 3.90% notes due 2039, and $1.5 billion of 4.00% notes due 2049. The Company used the net proceeds from the offering of $5.0 billion for general corporate purposes, including the repayment of outstanding commercial paper borrowings.

In 2018, Merck’s Board of Directors authorized purchases of up to $10 billion of Merck’s common stock for its treasury. The treasury stock purchase authorization has no time limit and will be made over time in open-market transactions, block transactions on or off an exchange, or in privately negotiated transactions. During the first nine months of 2020, the Company purchased $1.3 billion (16 million shares) of its common stock for its treasury under this share repurchase program. As of September 30, 2020, the Company’s remaining share repurchase authorization was $5.9 billion. In March 2020, the Company temporarily suspended its share repurchase program.

The Company has a $6.0 billion credit facility that matures in June 2024. The facility provides backup liquidity for the Company’s commercial paper borrowing facility and is to be used for general corporate purposes. The Company has not drawn funding from this facility.

Critical Accounting Policies

The Company’s significant accounting policies, which include management’s best estimates and judgments, are included in Note 2 to the consolidated financial statements for the year ended December 31, 2019 included in Merck’s Form 10‑K filed on February 26, 2020. Certain of these accounting policies are considered critical as disclosed in the Critical Accounting Policies section of Management’s Discussion and Analysis of Financial Condition and Results of Operations included in Merck’s Form 10-K because of the potential for a significant impact on the financial statements due to the inherent uncertainty in such estimates. There have been no significant changes in the Company’s critical accounting policies since December 31, 2019. See Note 1 to the condensed consolidated financial statements for information on the adoption of new accounting standards during 2020.

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Recently Issued Accounting Standards

For a discussion of recently issued accounting standards, see Note 1 to the condensed consolidated financial statements.

Item 4. Controls and Procedures

Management of the Company, with the participation of its Chief Executive Officer and Chief Financial Officer, has evaluated the effectiveness of the Company’s disclosure controls and procedures over financial reporting. Based on their evaluation, the Company’s Chief Executive Officer and Chief Financial Officer have concluded that as of September 30, 2020, the Company’s disclosure controls and procedures are effective. For the third quarter of 2020, there were no changes in internal control over financial reporting that materially affected, or are reasonably likely to materially affect, the Company’s internal control over financial reporting.

CAUTIONARY FACTORS THAT MAY AFFECT FUTURE RESULTS

This report and other written reports and oral statements made from time to time by the Company may contain so-called “forward-looking statements,” all of which are based on management’s current expectations and are subject to risks and uncertainties which may cause results to differ materially from those set forth in the statements. One can identify these forward-looking statements by their use of words such as “anticipates,” “expects,” “plans,” “will,” “estimates,” “forecasts,” “projects” and other words of similar meaning, or negative variations of any of the foregoing. One can also identify them by the fact that they do not relate strictly to historical or current facts. These statements are likely to address the Company’s growth strategy, financial results, product development, product approvals, product potential and development programs. One must carefully consider any such statement and should understand that many factors could cause actual results to differ materially from the Company’s forward-looking statements. These factors include inaccurate assumptions and a broad variety of other risks and uncertainties, including the impact of the global outbreak of COVID-19 and other risks and uncertainties some that are known and some that are not. No forward-looking statement can be guaranteed and actual future results may vary materially.

The Company does not assume the obligation to update any forward-looking statement. One should carefully evaluate such statements in light of factors, including risk factors, described in the Company’s filings with the Securities and Exchange Commission, especially on Forms 10-K, 10-Q and 8-K. In Item 1A. “Risk Factors” of the Company’s Annual Report on Form 10‑K for the year ended December 31, 2019, as filed on February 26, 2020, in the Company’s Form 10-Q for the quarterly period ended March 31, 2020, as filed on May 6, 2020, in the Company’s Form 10-Q for the quarterly period ended June 30, 2020, as filed on August 5, 2020, and in this Form 10-Q, the Company discusses in more detail various important risk factors that could cause actual results to differ from expected or historic results. The Company notes these factors for investors as permitted by the Private Securities Litigation Reform Act of 1995. One should understand that it is not possible to predict or identify all such factors. Consequently, the reader should not consider any such list to be a complete statement of all potential risks or uncertainties.

PART II - Other Information

Item 1. Legal Proceedings

The information called for by this Item is incorporated herein by reference to Note 9 included in Part I, Item 1, Financial Statements (unaudited) — Notes to Condensed Consolidated Financial Statements.

Item 1A. Risk Factors

For a discussion of risks that affect the Company’s business, please refer to Part I, Item IA, “Risk Factors” in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019. There have been no material changes to the risk factors as previously disclosed in the Company’s Annual Report on Form 10-K, except as follows:

The global COVID-19 pandemic is having an adverse impact on the Company’s business, operations and financial performance. The Company is unable to predict the full extent to which the pandemic and related impacts will continue to adversely impact its business, operations, financial performance, results of operations, and financial condition.

The Company’s business and financial results have been negatively impacted by the outbreak of Coronavirus Disease 2019 (COVID-19). The duration, spread and severity of the COVID-19 pandemic is uncertain, rapidly changing and difficult to predict. The degree to which COVID-19 impacts the Company’s results will depend on future developments, beyond the Company’s knowledge or control, including, but not limited to, the duration and spread of the outbreak, its

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severity, the actions taken to contain the virus or treat its impact, and how quickly and to what extent normal economic and operating conditions can resume.

Merck assumes that the majority of the negative impact from the COVID-19 pandemic occurred in the second quarter of 2020. However, the Company expects some residual negative impacts in the fourth quarter, largely in Europe and certain emerging markets. In addition, the phasing of the recovery of Gardasil 9 demand is slower than originally anticipated, in particular in the United States due to lower back-to-school demand. To the extent these assumptions prove to be incorrect, the Company’s results may differ materially from the estimates set forth herein.

Thus far in 2020, the COVID-19 pandemic has impacted the Company’s business and the Company continues to expect that it will impact the business in numerous ways, including but not limited to those outlined below:

In the third quarter of 2020, the negative impact of the COVID-19 pandemic to Merck’s Pharmaceutical sales was estimated to be approximately $475 million. The negative impact to Animal Health sales was immaterial. The negative impact to sales in the first nine months of 2020 was approximately $2.0 billion for the Pharmaceutical segment and $50 million for the Animal Health segment. For the full-year 2020, including the impact for the first nine months, Merck expects an unfavorable impact to sales of approximately $2.35 billion (excluding the impact of foreign exchange) due to the COVID-19 pandemic, comprised of approximately $2.3 billion for Pharmaceutical revenue and approximately $50 million for Animal Health revenue.

Roughly two-thirds of Merck’s Pharmaceutical revenue is comprised of physician-administered products, which, despite strong underlying demand, were affected by social distancing measures, fewer well visits and delays in elective surgeries due to the COVID-19 pandemic. These impacts, as well as the prioritization of COVID-19 patients at health care providers, have resulted in reduced administration of many of the Company’s human health products, in particular for its vaccines, including Gardasil 9 (Human Papillomavirus 9-valent Vaccine, Recombinant), as well as for Keytruda (pembrolizumab) and Implanon/Nexplanon (etonogestrel implant). Access to healthcare providers remains reduced, although improved from the second quarter. Merck anticipates reduced demand for its physician-administered products while pandemic-related access measures remain in place. In addition, declines in elective surgeries negatively affected the demand for Bridion (sugammadex) Injection in the year-to-date period. Sales of Pneumovax 23 (pneumococcal vaccine polyvalent) increased due to heightened awareness of pneumococcal vaccination during the COVID-19 pandemic and ahead of flu season.

Operating expenses were positively affected in the third quarter and first nine months of 2020 by approximately $115 million and $540 million, respectively, primarily driven by lower promotional and selling costs, as well as lower research and development expenses, net of investments in COVID-19-related antiviral and vaccine research programs. For the full-year 2020, Merck expects a net favorable impact to operating expenses of approximately $625 million reflecting continued lower spending due to the COVID-19 pandemic, partially offset by spending on COVID-19-related antiviral and vaccine research programs.

Item 2. Unregistered Sales of Equity Securities and Use of Proceeds

Issuer purchases of equity securities for the three months ended September 30, 2020 were as follows:

ISSUER PURCHASES OF EQUITY SECURITIES

															($ in millions)
Period			Total Number of Shares Purchased (1)						Average Price Paid Per Share						Approximate Dollar Value of Shares That May Yet Be Purchased Under the Plans or Programs (1)
July 1 - July 31			—						$0.00						$5,888
August 1 - August 31			—						$0.00						$5,888
September 1 - September 30			—						$0.00						$5,888
Total			—						$0.00						$5,888

(1) The Company did not purchase any shares during the three months ended September 30, 2020 under the plan approved by the Board of Directors in October 2018 to purchase up to $10 billion of Merck’s common stock for its treasury.

- 52 -

---

Item 6. Exhibits

Number						Description
3.1			—			Restated Certificate of Incorporation of Merck & Co., Inc. (November 3, 2009) – Incorporated by reference to Current Report on Form 8-K filed on November 4, 2009 (No. 1-6571)
3.2			—			By-Laws of Merck & Co., Inc. (effective July 22, 2015) – Incorporated by reference to Current Report on Form 8-K filed on July 28, 2015 (No. 1-6571)
31.1			—			Rule 13a – 14(a)/15d – 14(a) Certification of Chief Executive Officer
31.2			—			Rule 13a – 14(a)/15d – 14(a) Certification of Chief Financial Officer
32.1			—			Section 1350 Certification of Chief Executive Officer
32.2			—			Section 1350 Certification of Chief Financial Officer
101.INS			—			XBRL Instance Document - The instance document does not appear in the interactive data file because its XBRL tags are embedded within the Inline XBRL document.
101.SCH			—			XBRL Taxonomy Extension Schema Document.
101.CAL			—			XBRL Taxonomy Extension Calculation Linkbase Document.
101.DEF			—			XBRL Taxonomy Extension Definition Linkbase Document.
101.LAB			—			XBRL Taxonomy Extension Label Linkbase Document.
101.PRE			—			XBRL Taxonomy Extension Presentation Linkbase Document.
104			—			Cover Page Interactive Data File (formatted as Inline XBRL and contained in Exhibit 101).

- 53 -

---

Signatures

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

 

						MERCK & CO., INC.
Date: November 5, 2020						/s/ Jennifer Zachary
						JENNIFER ZACHARY
						Executive Vice President, General Counsel and Corporate Secretary
Date: November 5, 2020						/s/ Rita A. Karachun
						RITA A. KARACHUN
						Senior Vice President Finance - Global Controller

- 54 -

Exhibit 31.1

CERTIFICATION

I, Kenneth C. Frazier, certify that:

1.    I have reviewed this quarterly report on Form 10-Q of Merck & Co., Inc.;

2.    Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3.    Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4.    The registrant’s other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

a)    Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

b)    Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

c)    Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

d)    Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter (the registrant’s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and

5.    The registrant’s other certifying officer(s) and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions):

a)    All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize and report financial information; and

b)    Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.

Date: November 5, 2020

 

By:			/s/ Kenneth C. Frazier
			KENNETH C. FRAZIER Chairman, President and Chief Executive Officer

Exhibit 31.2

CERTIFICATION

I, Robert M. Davis, certify that:

1.    I have reviewed this quarterly report on Form 10-Q of Merck & Co., Inc.;

2.    Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

3.    Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

4.    The registrant’s other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

a)    Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

b)    Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

c)    Evaluated the effectiveness of the registrant’s disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

d)    Disclosed in this report any change in the registrant’s internal control over financial reporting that occurred during the registrant’s most recent fiscal quarter (the registrant’s fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting; and

5.    The registrant’s other certifying officer(s) and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant’s auditors and the audit committee of the registrant’s board of directors (or persons performing the equivalent functions):

a)    All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant’s ability to record, process, summarize and report financial information; and

b)    Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant’s internal control over financial reporting.

Date:   November 5, 2020

By:			/s/ Robert M. Davis
			ROBERT M. DAVIS Executive Vice President, Global Services and Chief Financial Officer

Exhibit 32.1

Section 1350

Certification of Chief Executive Officer

 

 

 

Pursuant to 18 U.S.C. Section 1350, the undersigned officer of Merck & Co., Inc. (the “Company”), hereby certifies that the Company's Quarterly Report on Form 10-Q for the quarter ended September 30, 2020 (the “Report”) fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934 and that the information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

Dated: November 5, 2020			/s/ Kenneth C. Frazier
			Name: Title:			KENNETH C. FRAZIER Chairman, President and Chief Executive Officer

Exhibit 32.2

Section 1350

Certification of Chief Financial Officer

Pursuant to 18 U.S.C. Section 1350, the undersigned officer of Merck & Co., Inc. (the “Company”), hereby certifies that the Company's Quarterly Report on Form 10-Q for the quarter ended September 30, 2020 (the “Report”) fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934 and that the information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

Dated: November 5, 2020			/s/ Robert M. Davis
			Name: Title:			ROBERT M. DAVIS Executive Vice President, Global Services and Chief Financial Officer

v3.20.2

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v3.20.2

CONDENSED CONSOLIDATED STATEMENT OF INCOME - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
Sales	$ 12,551	$ 12,397	$ 35,479	$ 34,972
Costs, Expenses and Other
Cost of sales	3,481	3,990	9,952	10,443
Selling, general and administrative	2,450	2,589	7,383	7,726
Research and development	3,390	3,204	7,721	7,324
Restructuring costs	114	232	269	444
Other (income) expense, net	(312)	35	(630)	362
Total Costs, Expenses and Other	9,123	10,050	24,695	26,299
Income Before Taxes	3,428	2,347	10,784	8,673
Taxes on Income	483	440	1,611	1,259
Net Income	2,945	1,907	9,173	7,414
Less: Net Income (Loss) Attributable to Noncontrolling Interests	4	6	12	(73)
Net Income Attributable to Merck & Co., Inc.	$ 2,941	$ 1,901	$ 9,161	$ 7,487
Basic Earnings per Common Share Attributable to Merck & Co., Inc. Common Shareholders (in dollars per share)	$ 1.16	$ 0.74	$ 3.62	$ 2.91
Earnings per Common Share Assuming Dilution Attributable to Merck & Co., Inc. Common Shareholders (in dollars per share)	$ 1.16	$ 0.74	$ 3.61	$ 2.89

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v3.20.2

CONDENSED CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net Income Attributable to Merck & Co., Inc.	$ 2,941	$ 1,901	$ 9,161	$ 7,487
Other Comprehensive Income (Loss) Net of Taxes:
Net unrealized (loss) gain on derivatives, net of reclassifications	(137)	91	(153)	(9)
Net unrealized (loss) gain on investments, net of reclassifications	0	(17)	(18)	109
Benefit plan net gain and prior service credit, net of amortization	62	15	161	41
Cumulative translation adjustment	85	(117)	(180)	14
Other comprehensive income (loss), net of taxes	10	(28)	(190)	155
Comprehensive Income Attributable to Merck & Co., Inc.	$ 2,951	$ 1,873	$ 8,971	$ 7,642

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v3.20.2

CONDENSED CONSOLIDATED BALANCE SHEET - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Current Assets
Cash and cash equivalents	$ 7,356	$ 9,676
Short-term investments	0	774
Accounts receivable (net of allowance for doubtful accounts of $89 in 2020 and $86 in 2019)	8,422	6,778
Inventories (excludes inventories of $2,081 in 2020 and $1,480 in 2019 classified in Other assets - see Note 6)	6,128	5,978
Other current assets	4,671	4,277
Total current assets	26,577	27,483
Investments	1,372	1,469
Property, Plant and Equipment, at cost, net of accumulated depreciation of $18,572 in 2020 and $17,686 in 2019	16,919	15,053
Goodwill	20,248	19,425
Other Intangibles, Net	16,677	14,196
Other Assets	8,007	6,771
Total Assets	89,800	84,397
Current Liabilities
Loans payable and current portion of long-term debt	2,420	3,610
Trade accounts payable	3,744	3,738
Accrued and other current liabilities	11,690	12,549
Income taxes payable	984	736
Dividends payable	1,567	1,587
Total current liabilities	20,405	22,220
Long-Term Debt	26,321	22,736
Deferred Income Taxes	1,777	1,470
Other Noncurrent Liabilities	12,027	11,970
Merck & Co., Inc. Stockholders’ Equity
Common stock, $0.50 par value Authorized - 6,500,000,000 shares Issued - 3,577,103,522 shares in 2020 and 2019	1,788	1,788
Other paid-in capital	39,489	39,660
Retained earnings	51,107	46,602
Accumulated other comprehensive loss	(6,383)	(6,193)
Stockholders' equity before deduction for treasury stock	86,001	81,857
Less treasury stock, at cost: 1,047,343,390 shares in 2020 and 1,038,087,496 shares in 2019	56,815	55,950
Total Merck & Co., Inc. stockholders’ equity	29,186	25,907
Noncontrolling Interests	84	94
Total equity	29,270	26,001
Liabilities and Equity	$ 89,800	$ 84,397

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- Definition The amount allocated to treasury stock. Treasury stock is common and preferred shares of an entity that were issued, repurchased by the entity, and are held in its treasury. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 30 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6405834&loc=d3e23315-112656 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.29,30) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6405813&loc=d3e23239-112655 + Details Name: us-gaap_TreasuryStockValue Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: instant

v3.20.2

CONDENSED CONSOLIDATED BALANCE SHEET (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 89	$ 86
Inventories classified in Other assets	2,081	1,480
Accumulated depreciation	$ 18,572	$ 17,686
Common stock, par value (in dollars per share)	$ 0.50	$ 0.50
Common stock, shares authorized (shares)	6,500,000,000	6,500,000,000
Common stock, shares issued (in shares)	3,577,103,522	3,577,103,522
Treasury Stock, Shares	1,047,343,390	1,038,087,496

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- Definition Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.14) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details Name: us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: instant

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- Definition Amount of allowance for credit loss on accounts receivable, classified as current. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(4) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=121611835&loc=d3e5074-111524 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=121599878&loc=SL82895884-210446 + Details Name: us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: instant

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- Definition Face amount or stated value per share of common stock. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details Name: us-gaap_CommonStockParOrStatedValuePerShare Namespace Prefix: us-gaap_ Data Type: num:perShareItemType Balance Type: na Period Type: instant

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- Definition The maximum number of common shares permitted to be issued by an entity's charter and bylaws. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details Name: us-gaap_CommonStockSharesAuthorized Namespace Prefix: us-gaap_ Data Type: xbrli:sharesItemType Balance Type: na Period Type: instant

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- Definition Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details Name: us-gaap_CommonStockSharesIssued Namespace Prefix: us-gaap_ Data Type: xbrli:sharesItemType Balance Type: na Period Type: instant

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- Definition Inventories not expected to be converted to cash, sold or exchanged within the normal operating cycle. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.6(d)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details Name: us-gaap_InventoryNoncurrent Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: instant

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- Definition Number of common and preferred shares that were previously issued and that were repurchased by the issuing entity and held in treasury on the financial statement date. This stock has no voting rights and receives no dividends. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.29,30) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6405813&loc=d3e23239-112655 + Details Name: us-gaap_TreasuryStockShares Namespace Prefix: us-gaap_ Data Type: xbrli:sharesItemType Balance Type: na Period Type: instant

v3.20.2

CONDENSED CONSOLIDATED STATEMENT OF CASH FLOWS - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash Flows from Operating Activities
Net income	$ 9,173	$ 7,414
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	2,721	2,716
Intangible asset impairment charges	35	864
Charge for acquisition of Peloton Therapeutics, Inc.	0	982
Deferred income taxes	47	(386)
Share-based compensation	354	306
Other	(445)	219
Net changes in assets and liabilities	(5,638)	(3,469)
Net Cash Provided by Operating Activities	6,247	8,646
Cash Flows from Investing Activities
Capital expenditures	(3,170)	(2,336)
Purchases of securities and other investments	(78)	(2,380)
Proceeds from sales of securities and other investments	1,894	7,459
Acquisition of ArQule, Inc., net of cash acquired	(2,545)	0
Acquisition of Antelliq Corporation, net of cash acquired	0	(3,620)
Acquisition of Peloton Therapeutics, Inc., net of cash acquired	0	(1,040)
Other acquisitions, net of cash acquired	(907)	(269)
Other	141	320
Net Cash Used in Investing Activities	(4,665)	(1,866)
Cash Flows from Financing Activities
Net change in short-term borrowings	(311)	(3,892)
Payments on debt	(1,954)	0
Proceeds from issuance of debt	4,419	4,958
Purchases of treasury stock	(1,281)	(3,730)
Dividends paid to stockholders	(4,673)	(4,290)
Proceeds from exercise of stock options	68	344
Other	(472)	(240)
Net Cash Used in Financing Activities	(4,204)	(6,850)
Effect of Exchange Rate Changes on Cash, Cash Equivalents and Restricted Cash	89	(26)
Net Decrease in Cash, Cash Equivalents and Restricted Cash	(2,533)	(96)
Cash, Cash Equivalents and Restricted Cash at Beginning of Year (includes restricted cash of $258 at January 1, 2020 included in Other Assets)	9,934	7,967
Cash, Cash Equivalents and Restricted Cash at End of Period (includes restricted cash of $45 at September 30, 2020 included in Other Assets)	$ 7,401	$ 7,871

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- Definition Amount of increase (decrease) in cash, cash equivalents, and cash and cash equivalents restricted to withdrawal or usage; including effect from exchange rate change. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 230 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=98513438&loc=d3e33268-110906 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3521-108585 + Details Name: us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: duration

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- Definition The increase (decrease) during the reporting period of all assets and liabilities used in operating activities. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585 + Details Name: us-gaap_IncreaseDecreaseInOperatingCapital Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: duration

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- References No definition available. + Details Name: us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract Namespace Prefix: us-gaap_ Data Type: xbrli:stringItemType Balance Type: na Period Type: duration

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- Definition Amount of income (expense) included in net income that results in no cash inflow (outflow), classified as other. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585 + Details Name: us-gaap_OtherNoncashIncomeExpense Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: duration

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- Definition The cash outflow to reacquire common stock during the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3291-108585 + Details Name: us-gaap_PaymentsForRepurchaseOfCommonStock Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: duration

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- Definition The cash outflow associated with a third acquisition of a business, net of the cash acquired from the purchase. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3213-108585 + Details Name: us-gaap_PaymentsToAcquireBusinessThreeNetOfCashAcquired Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: duration

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- Definition The cash outflow for purchases of and capital improvements on property, plant and equipment (capital expenditures), software, and other intangible assets. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3213-108585 + Details Name: us-gaap_PaymentsToAcquireProductiveAssets Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: duration

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- Definition The cash inflow from a debt initially having maturity due after one year or beyond the operating cycle, if longer. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3255-108585 + Details Name: us-gaap_ProceedsFromIssuanceOfLongTermDebt Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: duration

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- Definition The net cash inflow or outflow for borrowing having initial term of repayment within one year or the normal operating cycle, if longer. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 3 -Subparagraph (SX 210.12-04(a)) -URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e24072-122690 + Details Name: us-gaap_ProceedsFromRepaymentsOfShortTermDebt Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: duration

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- Definition The cash inflow associated with the sale, maturity and collection of all investments such as debt, security and so forth during the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3179-108585 + Details Name: us-gaap_ProceedsFromSaleMaturityAndCollectionsOfInvestments Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: duration

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- Definition Amount of cash inflow from exercise of option under share-based payment arrangement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=120381028&loc=SL79508275-113901 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3255-108585 + Details Name: us-gaap_ProceedsFromStockOptionsExercised Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: duration

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- Definition The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08(g)(1)(ii)) -URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 1A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121641772&loc=SL7669619-108580 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=109222650&loc=SL51721683-107760 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 250 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b)(2) -URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22499-107794 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 28 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=75031198&loc=d3e14064-108612 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=109239629&loc=SL4573702-111684 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 235 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-05(b)(2)) -URI http://asc.fasb.org/extlink&oid=120399901&loc=d3e537907-122884 Reference 8: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name 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-Section 50 -Paragraph 32 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599 Reference 13: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=109239629&loc=SL4573702-111684 Reference 14: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 55 -Paragraph 4J -URI http://asc.fasb.org/extlink&oid=120409616&loc=SL4591551-111686 Reference 15: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 30 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8906-108599 Reference 16: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3000-108585 Reference 17: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 45 -Paragraph 19 -URI http://asc.fasb.org/extlink&oid=108774443&loc=SL4569616-111683 Reference 18: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571 Reference 19: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 32 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599 Reference 20: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 55 -Paragraph 4K -URI 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- Definition The cash outflow for debt initially having maturity due after one year or beyond the normal operating cycle, if longer. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3291-108585 + Details Name: us-gaap_RepaymentsOfLongTermDebt Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: duration

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- Definition Amount of noncash expense for share-based payment arrangement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585 + Details Name: us-gaap_ShareBasedCompensation Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: duration

v3.20.2

CONDENSED CONSOLIDATED STATEMENT OF CASH FLOWS (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Statement of Cash Flows [Abstract]
Restricted cash	$ 45	$ 258

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v3.20.2

Basis of Presentation	9 Months Ended
	Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements of Merck & Co., Inc. (Merck or the Company) have been prepared pursuant to the rules and regulations for reporting on Form 10-Q. Accordingly, certain information and disclosures required by accounting principles generally accepted in the United States (GAAP) for complete consolidated financial statements are not included herein. These interim statements should be read in conjunction with the audited financial statements and notes thereto included in Merck’s Form 10-K filed on February 26, 2020. The results of operations of any interim period are not necessarily indicative of the results of operations for the full year. In the Company’s opinion, all adjustments necessary for a fair statement of these interim statements have been included and are of a normal and recurring nature. Planned Spin-Off of Women’s Health, Biosimilars and Established Brands into New Company In February 2020, Merck announced its intention to spin-off products from its women’s health, biosimilars and established brands businesses into a new, independent, publicly traded company named Organon & Co. (Organon) through a distribution of Organon’s publicly traded stock to Company shareholders. The distribution is expected to qualify as tax-free to the Company and its shareholders for U.S. federal income tax purposes. The established brands included in the transaction consist of dermatology, non-opioid pain management, respiratory, and select cardiovascular products including Zetia (ezetimibe) and Vytorin (ezetimibe and simvastatin), as well as the rest of Merck’s diversified brands franchise. Merck’s existing research pipeline programs will continue to be owned and developed within Merck as planned. Organon will have development capabilities initially focused on late-stage development and life-cycle management and is expected over time to develop research capabilities in selected therapeutic areas. The spin-off is expected to be completed in the second quarter of 2021, subject to market and certain other conditions. Subsequent to the spin-off, the historical results of the women’s health, biosimilars and established brands businesses will be reflected as discontinued operations in the Company’s consolidated financial statements. Recently Adopted Accounting Standards In June 2016, the Financial Accounting Standards Board (FASB) issued new guidance on the accounting for credit losses on financial instruments. The new guidance introduces an expected loss model for estimating credit losses, replacing the incurred loss model. The new guidance also changes the impairment model for available-for-sale debt securities, requiring the use of an allowance to record estimated credit losses (and subsequent recoveries). The Company adopted the new guidance effective January 1, 2020. There was no impact to the Company’s consolidated financial statements upon adoption. In November 2018, the FASB issued new guidance for collaborative arrangements intended to reduce diversity in practice by clarifying whether certain transactions between collaborative arrangement participants should be accounted for under revenue recognition guidance (ASC 606). The Company adopted the new guidance effective January 1, 2020, which resulted in minor changes to the presentation of information related to the Company’s collaborative arrangements. Recently Issued Accounting Standards Not Yet Adopted In December 2019, the FASB issued amended guidance on the accounting and reporting of income taxes. The guidance is intended to simplify the accounting for income taxes by: removing exceptions related to certain intraperiod tax allocations and deferred tax liabilities; clarifying guidance primarily related to evaluating the step-up tax basis for goodwill in a business combination; and reflecting enacted changes in tax laws or rates in the annual effective tax rate. The amended guidance is effective for interim and annual periods in 2021. Early adoption is permitted. The amendments in the new guidance are to be applied on a retrospective basis, on a modified retrospective basis through a cumulative-effect adjustment to retained earnings or prospectively, depending on the amendment. The Company is currently evaluating the impact of adoption on its consolidated financial statements. In January 2020, the FASB issued new guidance intended to clarify certain interactions between accounting standards related to equity securities, equity method investments and certain derivatives. The guidance addresses accounting for the transition into and out of the equity method of accounting and measuring certain purchased options and forward contracts to acquire investments. The new guidance is effective for interim and annual periods in 2021 and is to be applied prospectively. Early adoption is permitted. The Company is currently evaluating the impact of adoption on its consolidated financial statements. In March 2020, the FASB issued optional guidance to ease the potential burden in accounting for (or recognizing the effects of) reference rate reform on financial reporting. The guidance provides optional expedients and exceptions for applying GAAP to contracts, hedging relationships, and other transactions affected by reference rate reform. The optional guidance is effective upon issuance and can be applied on a prospective basis at any time between January 1, 2020 through December 31, 2022. The Company is currently evaluating the impact of adoption on its consolidated financial statements.

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v3.20.2

Acquisitions, Research Collaborations and License Agreements	9 Months Ended
	Sep. 30, 2020
Business Combinations [Abstract]
Acquisitions, Research Collaborations and License Agreements	Acquisitions, Research Collaborations and License Agreements The Company continues to pursue acquisitions and the establishment of external alliances such as research collaborations and licensing agreements to complement its internal research capabilities. These arrangements often include upfront payments, as well as expense reimbursements or payments to the third party, and milestone, royalty or profit share arrangements, contingent upon the occurrence of certain future events linked to the success of the asset in development. The Company also reviews its marketed products and pipeline to examine candidates which may provide more value through out-licensing and, as part of its portfolio assessment process, may also divest certain assets. Pro forma financial information for acquired businesses is not presented if the historical financial results of the acquired entity are not significant when compared with the Company’s financial results. In November 2020, Merck and VelosBio, Inc. (VelosBio) announced that the companies had entered into a definitive agreement pursuant to which Merck, through a subsidiary, will acquire all outstanding shares of VelosBio for $2.75 billion, subject to certain customary adjustments. VelosBio is a privately held clinical-stage biopharmaceutical company committed to developing first-in-class cancer therapies targeting receptor tyrosine kinase-like orphan receptor 1 (ROR1). VelosBio’s lead investigational candidate is VLS-101, an antibody-drug conjugate targeting ROR1 that is currently being evaluated in a Phase 1 and a Phase 2 clinical trial for the treatment of patients with hematologic malignancies and solid tumors, respectively. The closing of the transaction, which is subject to approval under the Hart-Scott-Rodino Antitrust Improvements Act and other customary conditions, is expected by the end of 2020. In September 2020, Merck and Seagen Inc. (Seagen, formerly known as Seattle Genetics, Inc.) announced an oncology collaboration to globally develop and commercialize Seagen’s ladiratuzumab vedotin (MK-6440), an investigational antibody-drug conjugate targeting LIV-1, which is currently in Phase 2 clinical trials for breast cancer and other solid tumors. The collaboration will pursue a broad joint development program evaluating ladiratuzumab vedotin as monotherapy and in combination with Keytruda (pembrolizumab) in triple-negative breast cancer, hormone receptor-positive breast cancer and other LIV-1-expressing solid tumors. The companies will equally share profits worldwide. Under the terms of the agreement, Merck made an upfront payment of $600 million and a $1.0 billion equity investment in 5 million shares of Seagen common stock at a price of $200 per share. Merck recorded $622 million in Research and development expenses in the third quarter and first nine months of 2020 related to this transaction reflecting the upfront payment as well as a $22 million mark-to-market loss on the purchase commitment (forward contract) relating to the equity shares (calculated based on the closing price of Seagen common stock on September 30, 2020). The closing of the equity investment occurred in October 2020 and resulted in the recognition of a $6 million reduction to Research and development expenses based on the price of Seagen common stock on the closing date. Seagen is also eligible to receive future contingent milestone payments of up to $2.6 billion, including $850 million in development milestones and $1.75 billion in sales milestones. Concurrent with the above transaction, Seagen granted Merck an exclusive license to commercialize Tukysa (tucatinib), a small molecule tyrosine kinase inhibitor, for the treatment of HER2-positive cancers, in Asia, the Middle East and Latin America and other regions outside of the United States, Canada and Europe. Merck will be responsible for marketing applications seeking approval in its territories, supported by the positive results from the HER2CLIMB clinical trial. Merck will also co-fund a portion of the Tukysa global development plan, which encompasses several ongoing and planned trials across HER2-positive cancers, including breast, colorectal, gastric and other cancers set forth in a global product development plan. Merck will solely fund and conduct country-specific clinical trials necessary to support anticipated regulatory applications in its territories. Under the terms of the agreement, Merck made upfront payments aggregating $210 million, which were recorded as Research and development expenses in the third quarter and first nine months of 2020. Seagen is also eligible to receive future contingent regulatory approval milestones of up to $65 million and will receive tiered royalties ranging from 20% to 33% based on annual sales levels of Tukysa in Merck’s territories. Additionally in September 2020, Merck acquired a biologics manufacturing facility located in Dunboyne, Ireland from Takeda Pharmaceutical Company Limited for €256 million ($302 million). The transaction was accounted for as an acquisition of an asset. Merck recorded property, plant and equipment of $289 million and other net assets of $13 million. There are no future contingent payments associated with the acquisition. In July 2020, Merck acquired the U.S. rights to Sentinel Flavor Tabs and Sentinel Spectrum Chews from Virbac Corporation for $410 million. Sentinel products provide protection against common parasites in dogs. The transaction was accounted for as an acquisition of an asset. Merck recognized intangible assets of $401 million related to currently marketed products and inventory of $9 million at the acquisition date. The estimated fair values of the identifiable intangible assets related to currently marketed products were determined using an income approach. Actual cash flows are likely to be different than those assumed. The intangible assets related to currently marketed products will be amortized over their estimated useful lives of 15 years. There are no future contingent payments associated with the acquisition. Also, in July 2020, Merck and Ridgeback Biotherapeutics LP (Ridgeback Bio), a closely held biotechnology company, closed a collaboration agreement to develop molnupiravir (MK-4482, formerly known as EIDD-2801), an orally available antiviral candidate currently in clinical development for the treatment of patients with COVID-19. Merck gained exclusive worldwide rights to develop and commercialize molnupiravir and related molecules. Under the terms of the agreement, Ridgeback Bio received an upfront payment and also is eligible to receive future contingent payments dependent upon the achievement of certain developmental and regulatory approval milestones, as well as a share of the net profits of molnupiravir and related molecules, if approved. Merck and Ridgeback are committed to ensure that any medicines developed for SARS-CoV-2 (the causative agent of COVID-19) will be accessible and affordable globally. In June 2020, Merck acquired privately held Themis Bioscience GmbH (Themis), a company focused on vaccines and immune-modulation therapies for infectious diseases and cancer for $366 million. Merck may make additional contingent payments of up to $740 million, including up to $80 million for development milestones, up to $260 million for regulatory approval milestones, and up to $400 million for commercial milestones. Themis has a broad pipeline of vaccine candidates and immune-modulatory therapies developed using its innovative measles virus vector platform based on a vector originally developed by scientists at the Institut Pasteur and licensed exclusively to Themis for select viral indications. The acquisition builds upon an ongoing collaboration between the two companies to develop vaccine candidates using the measles virus vector platform and is expected to accelerate the development of the COVID-19 vaccine candidate (V591), which is currently in Phase 1 clinical development. The transaction was accounted for as an acquisition of a business. The Company determined the fair value of the contingent consideration was $97 million at the acquisition date utilizing a probability-weighted estimated cash flow stream using an appropriate discount rate dependent on the nature and timing of the milestone payment. Merck recognized intangible assets for in-process research and development (IPR&D) of $136 million, cash of $59 million, deferred tax assets of $71 million and other net liabilities of $32 million. The excess of the consideration transferred over the fair value of net assets acquired of $229 million was recorded as goodwill that was allocated to the Pharmaceutical segment and is not deductible for tax purposes. The fair values of the identifiable intangible assets related to IPR&D were determined using an income approach. Actual cash flows are likely to be different than those assumed. In connection with the transaction, Merck has entered into a memorandum of understanding that reflects the parties’ commitments to address the COVID-19 pandemic by developing, manufacturing and distributing the vaccine on a global basis and with pricing that makes the vaccine both available around the world and accessible to those who need it. In May 2020, Merck and the International AIDS Vaccine Initiative, Inc. (IAVI), a nonprofit scientific research organization dedicated to addressing urgent, unmet global health challenges, announced a new collaboration to develop V590, an investigational vaccine against SARS-CoV-2 being studied for the prevention of COVID-19. This vaccine candidate will use the recombinant vesicular stomatitis virus (rVSV) technology that is the basis for Merck’s approved Ebola Zaire virus vaccine, Ervebo (Ebola Zaire Vaccine, Live), which was the first rVSV vaccine approved for use in humans. Under the terms of the agreement, Merck made an upfront payment of $6.5 million and may make additional contingent payments of up to $100 million for sales-based milestones, as well as royalty payments. Merck has also signed an agreement with the Biomedical Advanced Research and Development Authority (BARDA), part of the office of the Assistant Secretary for Preparedness and Response within an agency of the United States Department of Health and Human Services, to provide initial funding support for this effort. Under the agreement, IAVI and Merck will work together to advance the development and global clinical evaluation of a SARS-CoV-2 vaccine candidate designed and engineered by IAVI scientists. The vaccine candidate is currently in Phase 1 clinical development. Merck will lead regulatory filings globally. Both organizations will work together to develop the vaccine and make it accessible and affordable globally, if approved. In January 2020, Merck acquired ArQule, Inc. (ArQule), a publicly traded biopharmaceutical company focused on kinase inhibitor discovery and development for the treatment of patients with cancer and other diseases. Total consideration paid of $2.7 billion included $138 million of share-based compensation payments to settle equity awards attributable to precombination service and cash paid for transaction costs on behalf of ArQule. The Company incurred $95 million of transaction costs directly related to the acquisition of ArQule, consisting almost entirely of share-based compensation payments to settle non-vested equity awards attributable to postcombination service. These costs were included in Selling, general and administrative expenses in the first nine months of 2020. ArQule’s lead investigational candidate, MK-1026 (formerly known as ARQ 531), is a novel, oral Bruton’s tyrosine kinase (BTK) inhibitor currently being evaluated for the treatment of B-cell malignancies. The estimated fair value of assets acquired and liabilities assumed from ArQule is as follows: ($ in millions) January 16, 2020 Cash and cash equivalents $ 145  IPR&D MK-1026 (formerly ARQ 531) (1) 2,280  Licensing arrangement for ARQ 087 80  Deferred income tax liabilities (389) Other assets and liabilities, net 34  Total identifiable net assets 2,150  Goodwill (2) 540  Consideration transferred $ 2,690  (1)    The estimated fair value of the identifiable intangible asset related to IPR&D was determined using an income approach. The future net cash flows were discounted to present value utilizing a discount rate of 12.5%. Actual cash flows are likely to be different than those assumed. (2)    The goodwill was allocated to the Pharmaceutical segment and is not deductible for tax purposes. In July 2019, Merck acquired Peloton Therapeutics, Inc. (Peloton), a clinical-stage biopharmaceutical company focused on the development of novel small molecule therapeutic candidates targeting hypoxia-inducible factor-2α (HIF-2α) for the treatment of patients with cancer and other non-oncology diseases. Peloton’s lead candidate, MK-6482 (formerly known as PT2977), is a novel investigational oral HIF-2α inhibitor in late-stage development for renal cell carcinoma. Merck made an upfront payment of $1.2 billion; additionally, former Peloton shareholders will be eligible to receive $50 million upon U.S. regulatory approval, $50 million upon first commercial sale in the United States, and up to $1.05 billion of sales-based milestones. The transaction was accounted for as an acquisition of an asset. Merck recorded cash of $157 million, deferred tax liabilities of $64 million, and other net liabilities of $6 million at the acquisition date and Research and development expenses of $982 million in the third quarter and first nine months of 2019 related to the transaction. On April 1, 2019, Merck acquired Antelliq Corporation (Antelliq), a leader in digital animal identification, traceability and monitoring solutions. These solutions help veterinarians, farmers and pet owners gather critical data to improve management, health and well-being of livestock and pets. Merck paid $2.3 billion to acquire all outstanding shares of Antelliq and spent $1.3 billion to repay Antelliq’s debt. The transaction was accounted for as an acquisition of a business. The estimated fair value of assets acquired and liabilities assumed from Antelliq is as follows: ($ in millions) April 1, 2019 Cash and cash equivalents $ 31  Accounts receivable 73  Inventories 93  Property, plant and equipment 60  Identifiable intangible assets (useful lives ranging from 18-24 years) (1) 2,689  Deferred income tax liabilities (589) Other assets and liabilities, net (82) Total identifiable net assets 2,275  Goodwill (2) 1,376  Consideration transferred $ 3,651  (1)    The estimated fair values of identifiable intangible assets relate primarily to trade names and were determined using an income approach. The future net cash flows were discounted to present value utilizing a discount rate of 11.5%. Actual cash flows are likely to be different than those assumed. (2)    The goodwill recognized is largely attributable to anticipated synergies expected to arise after the acquisition and was allocated to the Animal Health segment. The goodwill is not deductible for tax purposes. The Company’s results for the first nine months of 2019 include five months of activity for Antelliq. The Company incurred $47 million of transaction costs directly related to the acquisition of Antelliq, consisting largely of advisory fees, which are reflected in Selling, general and administrative expenses in the first nine months of 2019. Also in April 2019, Merck acquired Immune Design, a late-stage immunotherapy company employing next-generation in vivo approaches to enable the body’s immune system to fight disease, for $301 million in cash. The transaction was accounted for as an acquisition of a business. Merck recognized intangible assets of $156 million, cash of $83 million and other net assets of $42 million. The excess of the consideration transferred over the fair value of net assets acquired of $20 million was recorded as goodwill that was allocated to the Pharmaceutical segment and is not deductible for tax purposes. The fair values of the identifiable intangible assets related to IPR&D were determined using an income approach. Actual cash flows are likely to be different than those assumed.

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- Definition Information related to acquisitions, divestitures, research collaborations and license agreements. + References No definition available. + Details Name: mrk_AcquisitionsResearchCollaborationsAndLicenseAgreementsTextBlock Namespace Prefix: mrk_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

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- References No definition available. + Details Name: us-gaap_BusinessCombinationsAbstract Namespace Prefix: us-gaap_ Data Type: xbrli:stringItemType Balance Type: na Period Type: duration

v3.20.2

Collaborative Arrangements	9 Months Ended
	Sep. 30, 2020
Collaborative Arrangements [Abstract]
Collaborative Arrangements	Collaborative Arrangements Merck has entered into collaborative arrangements that provide the Company with varying rights to develop, produce and market products together with its collaborative partners. Both parties in these arrangements are active participants and exposed to significant risks and rewards dependent on the commercial success of the activities of the collaboration. Merck’s more significant collaborative arrangements are discussed below. AstraZeneca In July 2017, Merck and AstraZeneca PLC (AstraZeneca) entered into a global strategic oncology collaboration to co-develop and co-commercialize AstraZeneca’s Lynparza (olaparib) for multiple cancer types. Lynparza is an oral poly (ADP-ribose) polymerase (PARP) inhibitor currently approved for certain types of advanced ovarian, breast, pancreatic and prostate cancers. The companies are jointly developing and commercializing Lynparza, both as monotherapy and in combination trials with other potential medicines. Independently, Merck and AstraZeneca will develop and commercialize Lynparza in combinations with their respective PD-1 and PD-L1 medicines, Keytruda and Imfinzi. The companies will also jointly develop and commercialize AstraZeneca’s Koselugo (selumetinib), an oral, selective inhibitor of MEK, part of the mitogen-activated protein kinase (MAPK) pathway, currently being developed for multiple indications. In April 2020, Koselugo was approved by the U.S. Food and Drug Administration (FDA) for the treatment of pediatric patients two years of age and older with neurofibromatosis type 1 who have symptomatic, inoperable plexiform neurofibromas. Under the terms of the agreement, AstraZeneca and Merck will share the development and commercialization costs for Lynparza and Koselugo monotherapy and non-PD-L1/PD-1 combination therapy opportunities. Profits from Lynparza and Koselugo product sales generated through monotherapies or combination therapies are shared equally. Merck will fund all development and commercialization costs of Keytruda in combination with Lynparza or Koselugo. AstraZeneca will fund all development and commercialization costs of Imfinzi in combination with Lynparza or Koselugo. AstraZeneca is the principal on Lynparza and Koselugo sales transactions. Merck records its share of Lynparza and Koselugo product sales, net of cost of sales and commercialization costs, as alliance revenue and its share of development costs associated with the collaboration as part of Research and development expenses. Reimbursements received from AstraZeneca for research and development expenses are recognized as reductions to Research and development costs. As part of the agreement, Merck made an upfront payment to AstraZeneca of $1.6 billion in 2017 and made payments of $750 million over a multi-year period for certain license options. In addition, the agreement provides for additional contingent payments from Merck to AstraZeneca related to the successful achievement of sales-based and regulatory milestones. In the second quarter of 2020, Merck determined it was probable that sales of Lynparza in the future would trigger $400 million of sales-based milestone payments from Merck to AstraZeneca. Accordingly, Merck recorded a $400 million liability and a corresponding increase to the intangible asset related to Lynparza. Prior to 2020, Merck accrued sales-based milestone payments aggregating $1.0 billion related to Lynparza, of which $200 million and $250 million was paid to AstraZeneca in 2019 and 2018, respectively, and $250 million was paid in the first nine months of 2020. Potential future sales-based milestone payments of $2.7 billion have not yet been accrued as they are not deemed by the Company to be probable at this time. In the second quarter of 2020, Lynparza received regulatory approvals triggering capitalized milestone payments of $135 million from Merck to AstraZeneca. In 2019 and 2018, Lynparza received regulatory approvals triggering capitalized milestone payments of $60 million and $140 million, respectively, in the aggregate from Merck to AstraZeneca. Potential future regulatory milestone payments of $1.4 billion remain under the agreement. The intangible asset balance related to Lynparza (which includes capitalized sales-based and regulatory milestone payments) was $1.3 billion at September 30, 2020 and is included in Other Intangibles, Net on the Consolidated Balance Sheet. The amount is being amortized over its estimated useful life through 2028 as supported by projected future cash flows, subject to impairment testing. Summarized financial information related to this collaboration is as follows: Three Months Ended September 30, Nine Months Ended September 30, ($ in millions) 2020 2019 2020 2019 Alliance revenue - Lynparza $ 196  $ 123  $ 519  $ 313  Alliance revenue - Koselugo 3  —  3  —  Total alliance revenue $ 199  $ 123  $ 522  $ 313  Cost of sales (1) 41  28  205  120  Selling, general and administrative 40  36  112  96  Research and development 20  44  93  122  ($ in millions) September 30, 2020 December 31, 2019 Receivables from AstraZeneca included in Other current assets $ 197  $ 128  Payables to AstraZeneca included in Accrued and other current liabilities (2) 309  577  Payables to AstraZeneca included in Other Noncurrent Liabilities (2) 400  —  (1) Represents amortization of capitalized milestone payments. (2) Includes accrued milestone payments. Eisai In March 2018, Merck and Eisai Co., Ltd. (Eisai) announced a strategic collaboration for the worldwide co-development and co-commercialization of Lenvima (lenvatinib), an orally available tyrosine kinase inhibitor discovered by Eisai. Lenvima is currently approved for the treatment of certain types of thyroid cancer, hepatocellular carcinoma, in combination with everolimus for certain patients with renal cell carcinoma, and in combination with Keytruda for the treatment of certain patients with endometrial carcinoma. Under the agreement, Merck and Eisai will develop and commercialize Lenvima jointly, both as monotherapy and in combination with Keytruda. Eisai records Lenvima product sales globally (Eisai is the principal on Lenvima sales transactions), and Merck and Eisai share profits equally. Merck records its share of Lenvima product sales, net of cost of sales and commercialization costs, as alliance revenue. Expenses incurred during co-development, including for studies evaluating Lenvima as monotherapy, are shared equally by the two companies and reflected in Research and development expenses. Under the agreement, Merck made an upfront payment to Eisai of $750 million and agreed to make payments of up to $650 million for certain option rights through 2021 (of which $325 million was paid in March 2019, $200 million was paid in March 2020 and $125 million is expected to be paid in March 2021). In addition, the agreement provides for additional contingent payments from Merck to Eisai related to the successful achievement of sales-based and regulatory milestones. In the second quarter of 2020, Merck determined it was probable that sales of Lenvima in the future would trigger sales-based milestone payments aggregating $370 million from Merck to Eisai. Accordingly, Merck recorded a $370 million liability and a corresponding increase to the intangible asset related to Lenvima. Prior to 2020, Merck accrued sales-based milestone payments aggregating $950 million. Of these amounts, $50 million was paid to Eisai in 2019 and an additional $500 million was paid in the first nine months of 2020. Potential future sales-based milestone payments of $2.7 billion have not yet been accrued as they are not deemed by the Company to be probable at this time. In 2018, Lenvima received regulatory approvals triggering capitalized milestone payments of $250 million in the aggregate from Merck to Eisai. Potential future regulatory milestone payments of $135 million remain under the agreement. The intangible asset balance related to Lenvima (which includes capitalized sales-based and regulatory milestone payments) was $1.1 billion at September 30, 2020 and is included in Other Intangibles, Net on the Consolidated Balance Sheet. The amount is being amortized over its estimated useful life through 2026 as supported by projected future cash flows, subject to impairment testing. Summarized financial information related to this collaboration is as follows: Three Months Ended September 30, Nine Months Ended September 30, ($ in millions) 2020 2019 2020 2019 Alliance revenue - Lenvima $ 142  $ 109  $ 421  $ 280  Cost of sales (1) 46  23  215  97  Selling, general and administrative 18  21  48  59  Research and development 48  37  168  146  ($ in millions) September 30, 2020 December 31, 2019 Receivables from Eisai included in Other current assets $ 170  $ 150  Payables to Eisai included in Accrued and other current liabilities (2) 325  700  Payables to Eisai included in Other Noncurrent Liabilities (3) 570  525  (1) Represents amortization of capitalized milestone payments. (2) Includes accrued milestone and future option payments. (3) Includes accrued milestone payments. Bayer AG In 2014, the Company entered into a worldwide clinical development collaboration with Bayer AG (Bayer) to market and develop soluble guanylate cyclase (sGC) modulators including Bayer’s Adempas (riociguat), which is approved to treat pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension. The two companies have implemented a joint development and commercialization strategy. The collaboration also includes clinical development of Bayer’s vericiguat, which is in development for the potential treatment of worsening heart failure. Vericiguat is currently under review by regulatory authorities in the United States, the EU and Japan. Under the agreement, Bayer leads commercialization of Adempas in the Americas, while Merck leads commercialization in the rest of the world. For vericiguat, if approved, Bayer will lead commercialization in the rest of world and Merck will lead in the Americas. Both companies share in development costs and profits on sales and have the right to co-promote in territories where they are not the lead. Merck records sales of Adempas in its marketing territories, as well as alliance revenue, which is Merck’s share of profits from the sale of Adempas in Bayer’s marketing territories. In addition, the agreement provides for contingent payments from Merck to Bayer related to the successful achievement of sales-based milestones. Prior to 2020, Merck accrued $725 million of sales-based milestone payments for this collaboration, of which $350 million was paid to Bayer in 2018. There is an additional $400 million potential future sales-based milestone payment that has not yet been accrued as it is not deemed by the Company to be probable at this time. The intangible asset balance related to this collaboration (which includes the acquired intangible asset balance, as well as capitalized sales-based milestone payments) was $838 million at September 30, 2020 and is included in Other Intangibles, Net on the Consolidated Balance Sheet. The amount is being amortized over its estimated useful life through 2027 as supported by projected future cash flows, subject to impairment testing. Summarized financial information related to this collaboration is as follows: Three Months Ended September 30, Nine Months Ended September 30, ($ in millions) 2020 2019 2020 2019 Alliance revenue - Adempas $ 83  $ 50  $ 216  $ 144  Net sales of Adempas recorded by Merck 55  57  167  158  Total sales $ 138  $ 107  $ 383  $ 302  Cost of sales (1) 29  28  85  86  Selling, general and administrative 19  12  42  31  Research and development 12  31  53  94  ($ in millions) September 30, 2020 December 31, 2019 Receivables from Bayer included in Other current assets $ 70  $ 49  Payables to Bayer included in Other Noncurrent Liabilities (2) 375  375  (1) Includes amortization of intangible assets. (2) Represents accrued milestone payment.

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- Definition Collaborative Arrangements [Abstract] + References No definition available. + Details Name: mrk_CollaborativeArrangementsAbstract Namespace Prefix: mrk_ Data Type: xbrli:stringItemType Balance Type: na Period Type: duration

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- Definition The entire disclosure for collaborative arrangements in which the entity is a participant, including a) information about the nature and purpose of such arrangements; b) its rights and obligations thereunder; c) the accounting policy for collaborative arrangements; and d) the income statement classification and amounts attributable to transactions arising from the collaborative arrangement between participants. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 808 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6931272&loc=SL5834143-161434 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 808 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6931272&loc=SL5834143-161434 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 808 -URI http://asc.fasb.org/topic&trid=5833765 + Details Name: us-gaap_CollaborativeArrangementDisclosureTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

v3.20.2

Restructuring	9 Months Ended
	Sep. 30, 2020
Restructuring and Related Activities [Abstract]
Restructuring	Restructuring In early 2019, Merck approved a new global restructuring program (Restructuring Program) as part of a worldwide initiative focused on further optimizing the Company’s manufacturing and supply network, as well as reducing its global real estate footprint. This program is a continuation of the Company’s plant rationalization, builds on prior restructuring programs and does not include any actions associated with the planned spin-off of Organon. As the Company continues to evaluate its global footprint and overall operating model, it subsequently identified additional actions under the Restructuring Program, and could identify further actions over time. The actions currently contemplated under the Restructuring Program are expected to be substantially completed by the end of 2023, with the cumulative pretax costs to be incurred by the Company to implement the program estimated to be approximately $2.5 billion. The Company estimates that approximately 60% of the cumulative pretax costs will result in cash outlays, primarily related to employee separation expense and facility shut-down costs. Approximately 40% of the cumulative pretax costs will be non-cash, relating primarily to the accelerated depreciation of facilities to be closed or divested. The Company expects to record charges of approximately $800 million in 2020 related to the Restructuring Program. Actions under previous global restructuring programs have been substantially completed. The Company recorded total pretax costs of $186 million and $296 million in the third quarter of 2020 and 2019, respectively, and $504 million and $642 million for the first nine months of 2020 and 2019, respectively, related to restructuring program activities. Since inception of the Restructuring Program through September 30, 2020, Merck has recorded total pretax accumulated costs of approximately $1.4 billion. For segment reporting, restructuring charges are unallocated expenses. The following tables summarize the charges related to restructuring program activities by type of cost:   Three Months Ended September 30, 2020 Nine Months Ended September 30, 2020 ($ in millions) Separation Costs Accelerated Depreciation Other Total Separation Costs Accelerated Depreciation Other Total Cost of sales $ —  $ 33  $ 5  $ 38  $ —  $ 89  $ 42  $ 131  Selling, general and administrative —  15  —  15  —  37  —  37  Research and development —  18  1  19  —  66  1  67  Restructuring costs 61  —  53  114  143  —  126  269  $ 61  $ 66  $ 59  $ 186  $ 143  $ 192  $ 169  $ 504    Three Months Ended September 30, 2019 Nine Months Ended September 30, 2019 ($ in millions) Separation Costs Accelerated Depreciation Other Total Separation Costs Accelerated Depreciation Other Total Cost of sales $ —  $ 41  $ 21  $ 62  $ —  $ 139  $ 22  $ 161  Selling, general and administrative —  1  —  1  —  33  —  33  Research and development —  (1) 2  1  —  1  3  4  Restructuring costs 205  —  27  232  358  —  86  444  $ 205  $ 41  $ 50  $ 296  $ 358  $ 173  $ 111  $ 642  Separation costs are associated with actual headcount reductions, as well as those headcount reductions which were probable and could be reasonably estimated. Accelerated depreciation costs primarily relate to manufacturing, research and administrative facilities and equipment to be sold or closed as part of the programs. Accelerated depreciation costs represent the difference between the depreciation expense to be recognized over the revised useful life of the asset, based upon the anticipated date the site will be closed or divested or the equipment disposed of, and depreciation expense as determined utilizing the useful life prior to the restructuring actions. All the sites have and will continue to operate up through the respective closure dates and, since future undiscounted cash flows are sufficient to recover the respective book values, Merck is recording accelerated depreciation over the revised useful life of the site assets. Anticipated site closure dates, particularly related to manufacturing locations, have been and may continue to be adjusted to reflect changes resulting from regulatory or other factors. Other activity in 2020 and 2019 includes asset abandonment, facility shut-down and other related costs, as well as pretax gains and losses resulting from the sales of facilities and related assets. Additionally, other activity includes certain employee-related costs associated with pension and other postretirement benefit plans (see Note 12) and share-based compensation. The following table summarizes the charges and spending relating to restructuring program activities for the nine months ended September 30, 2020: ($ in millions) Separation Costs Accelerated Depreciation Other Total Restructuring reserves January 1, 2020 $ 690  $ —  $ 69  $ 759  Expense 143  192  169  504  (Payments) receipts, net (395) —  (237) (632) Non-cash activity —  (192) 39  (153) Restructuring reserves September 30, 2020 (1) $ 438  $ —  $ 40  $ 478  (1)The remaining cash outlays are expected to be substantially completed by the end of 2023.

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- Definition The entire disclosure for restructuring and related activities. Description of restructuring activities such as exit and disposal activities, include facts and circumstances leading to the plan, the expected plan completion date, the major types of costs associated with the plan activities, total expected costs, the accrual balance at the end of the period, and the periods over which the remaining accrual will be settled. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -URI http://asc.fasb.org/topic&trid=2175745 + Details Name: us-gaap_RestructuringAndRelatedActivitiesDisclosureTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

v3.20.2

Financial Instruments	9 Months Ended
	Sep. 30, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Financial Instruments	Financial Instruments Derivative Instruments and Hedging Activities The Company manages the impact of foreign exchange rate movements and interest rate movements on its earnings, cash flows and fair values of assets and liabilities through operational means and through the use of various financial instruments, including derivative instruments. A significant portion of the Company’s revenues and earnings in foreign affiliates is exposed to changes in foreign exchange rates. The objectives and accounting related to the Company’s foreign currency risk management program, as well as its interest rate risk management activities are discussed below. Foreign Currency Risk Management The Company has established revenue hedging, balance sheet risk management and net investment hedging programs to protect against volatility of future foreign currency cash flows and changes in fair value caused by changes in foreign exchange rates. The objective of the revenue hedging program is to reduce the variability caused by changes in foreign exchange rates that would affect the U.S. dollar value of future cash flows derived from foreign currency denominated sales, primarily the euro, Japanese yen and Chinese renminbi. To achieve this objective, the Company will hedge a portion of its forecasted foreign currency denominated third-party and intercompany distributor entity sales (forecasted sales) that are expected to occur over its planning cycle, typically no more than two years into the future. The Company will layer in hedges over time, increasing the portion of forecasted sales hedged as it gets closer to the expected date of the forecasted sales. The portion of forecasted sales hedged is based on assessments of cost-benefit profiles that consider natural offsetting exposures, revenue and exchange rate volatilities and correlations, and the cost of hedging instruments. The Company manages its anticipated transaction exposure principally with purchased local currency put options, forward contracts and purchased collar options. The fair values of these derivative contracts are recorded as either assets (gain positions) or liabilities (loss positions) in the Condensed Consolidated Balance Sheet. Changes in the fair value of derivative contracts are recorded each period in either current earnings or Other comprehensive income (OCI), depending on whether the derivative is designated as part of a hedge transaction and, if so, the type of hedge transaction. For derivatives that are designated as cash flow hedges, the unrealized gains or losses on these contracts are recorded in Accumulated other comprehensive income (AOCI) and reclassified into Sales when the hedged anticipated revenue is recognized. For those derivatives which are not designated as cash flow hedges, but serve as economic hedges of forecasted sales, unrealized gains or losses are recorded in Sales each period. The cash flows from both designated and non-designated contracts are reported as operating activities in the Condensed Consolidated Statement of Cash Flows. The Company does not enter into derivatives for trading or speculative purposes. The Company manages operating activities and net asset positions at each local subsidiary in order to mitigate the effects of exchange on monetary assets and liabilities. The Company also uses a balance sheet risk management program to mitigate the exposure of net monetary assets that are denominated in a currency other than a subsidiary’s functional currency from the effects of volatility in foreign exchange. In these instances, Merck principally utilizes forward exchange contracts to offset the effects of exchange on exposures denominated in developed country currencies, primarily the euro and Japanese yen. For exposures in developing country currencies, the Company will enter into forward contracts to partially offset the effects of exchange on exposures when it is deemed economical to do so based on a cost-benefit analysis that considers the magnitude of the exposure, the volatility of the exchange rate and the cost of the hedging instrument. The cash flows from these contracts are reported as operating activities in the Condensed Consolidated Statement of Cash Flows. Monetary assets and liabilities denominated in a currency other than the functional currency of a given subsidiary are remeasured at spot rates in effect on the balance sheet date with the effects of changes in spot rates reported in Other (income) expense, net. The forward contracts are not designated as hedges and are marked to market through Other (income) expense, net. Accordingly, fair value changes in the forward contracts help mitigate the changes in the value of the remeasured assets and liabilities attributable to changes in foreign currency exchange rates, except to the extent of the spot-forward differences. These differences are not significant due to the short-term nature of the contracts, which typically have average maturities at inception of less than one year. The Company also uses forward exchange contracts to hedge a portion of its net investment in foreign operations against movements in exchange rates. The forward contracts are designated as hedges of the net investment in a foreign operation. The unrealized gains or losses on these contracts are recorded in foreign currency translation adjustment within OCI and remain in AOCI until either the sale or complete or substantially complete liquidation of the subsidiary. The Company excludes certain portions of the change in fair value of its derivative instruments from the assessment of hedge effectiveness (excluded components). Changes in fair value of the excluded components are recognized in OCI. The Company recognizes in earnings the initial value of the excluded components on a straight-line basis over the life of the derivative instrument, rather than using the mark-to-market approach. The cash flows from these contracts are reported as investing activities in the Condensed Consolidated Statement of Cash Flows. Foreign exchange risk is also managed through the use of foreign currency debt. The Company’s senior unsecured euro-denominated notes have been designated as, and are effective as, economic hedges of the net investment in a foreign operation. Accordingly, foreign currency transaction gains or losses due to spot rate fluctuations on the euro-denominated debt instruments are included in foreign currency translation adjustment within OCI. The effects of the Company’s net investment hedges on OCI and the Consolidated Statement of Income are shown below: Amount of Pretax (Gain) Loss Recognized in Other Comprehensive Income (1) Amount of Pretax (Gain) Loss Recognized in Other (income) expense, net for Amounts Excluded from Effectiveness Testing Three Months Ended September 30, Nine Months Ended September 30, Three Months Ended September 30, Nine Months Ended September 30, ($ in millions) 2020 2019 2020 2019 2020 2019 2020 2019 Net Investment Hedging Relationships Foreign exchange contracts $ 10  $ 1  $ 15  $ 8  $ (4) $ (8) $ (15) $ (23) Euro-denominated notes 162  (150) 182  (152) —  —  —  —  (1) No amounts were reclassified from AOCI into income related to the sale of a subsidiary. Interest Rate Risk Management The Company may use interest rate swap contracts on certain investing and borrowing transactions to manage its net exposure to interest rate changes and to reduce its overall cost of borrowing. The Company does not use leveraged swaps and, in general, does not leverage any of its investment activities that would put principal capital at risk. In February 2020, five interest rate swaps with notional amounts of $250 million each matured. These swaps effectively converted the Company’s $1.25 billion, 1.85% fixed-rate notes due 2020 to variable rate debt. At September 30, 2020, the Company was a party to 14 pay-floating, receive-fixed interest rate swap contracts designated as fair value hedges of fixed-rate notes in which the notional amounts match the amount of the hedged fixed-rate notes as detailed in the table below. September 30, 2020 ($ in millions) Par Value of Debt Number of Interest Rate Swaps Held Total Swap Notional Amount 3.875% notes due 2021 $ 1,150  5  $ 1,150  2.40% notes due 2022 1,000  4  1,000  2.35% notes due 2022 1,250  5  1,250  The interest rate swap contracts are designated hedges of the fair value changes in the notes attributable to changes in the benchmark London Interbank Offered Rate (LIBOR) swap rate. The fair value changes in the notes attributable to changes in the LIBOR swap rate are recorded in interest expense along with the offsetting fair value changes in the swap contracts. The cash flows from these contracts are reported as operating activities in the Condensed Consolidated Statement of Cash Flows. The table below presents the location of amounts recorded on the Consolidated Balance Sheet related to cumulative basis adjustments for fair value hedges: Carrying Amount of Hedged Liabilities Cumulative Amount of Fair Value Hedging Adjustment Increase (Decrease) Included in the Carrying Amount ($ in millions) September 30, 2020 December 31, 2019 September 30, 2020 December 31, 2019 Balance Sheet Line Item in which Hedged Item is Included Loans payable and current portion of long-term debt $ 1,155  $ 1,249  $ 5  $ (1) Long-Term Debt 2,309  3,409  62  14  Presented in the table below is the fair value of derivatives on a gross basis segregated between those derivatives that are designated as hedging instruments and those that are not designated as hedging instruments:     September 30, 2020 December 31, 2019     Fair Value of Derivative U.S. Dollar Notional Fair Value of Derivative U.S. Dollar Notional ($ in millions) Balance Sheet Caption Asset Liability Asset Liability Derivatives Designated as Hedging Instruments Interest rate swap contracts Other current assets $ 6  $ —  $ 1,150  $ —  $ —  $ —  Interest rate swap contracts Other Assets 63  —  2,250  15  —  3,400  Interest rate swap contracts Accrued and other current liabilities —  —  —  —  1  1,250  Foreign exchange contracts Other current assets 30  —  4,120  152  —  6,117  Foreign exchange contracts Other Assets 59  —  1,881  55  —  2,160  Foreign exchange contracts Accrued and other current liabilities —  104  3,096  —  22  1,748  Foreign exchange contracts Other Noncurrent Liabilities —  1  157  —  1  53      $ 158  $ 105  $ 12,654  $ 222  $ 24  $ 14,728  Derivatives Not Designated as Hedging Instruments               Foreign exchange contracts Other current assets $ 81  $ —  $ 5,455  $ 66  $ —  $ 7,245  Foreign exchange contracts Accrued and other current liabilities —  171  8,042  —  73  8,693  Forward contract related to Seagen common stock Accrued and other current liabilities —  22  1,000  —  —  —      $ 81  $ 193  $ 14,497  $ 66  $ 73  $ 15,938      $ 239  $ 298  $ 27,151  $ 288  $ 97  $ 30,666  As noted above, the Company records its derivatives on a gross basis in the Condensed Consolidated Balance Sheet. The Company has master netting agreements with several of its financial institution counterparties (see Concentrations of Credit Risk below). The following table provides information on the Company’s derivative positions subject to these master netting arrangements as if they were presented on a net basis, allowing for the right of offset by counterparty and cash collateral exchanged per the master agreements and related credit support annexes:   September 30, 2020 December 31, 2019 ($ in millions) Asset Liability Asset Liability Gross amounts recognized in the condensed consolidated balance sheet $ 239  $ 298  $ 288  $ 97  Gross amounts subject to offset in master netting arrangements not offset in the condensed consolidated balance sheet (140) (140) (84) (84) Cash collateral received —  —  (34) —  Net amounts $ 99  $ 158  $ 170  $ 13  The table below provides information regarding the location and amount of pretax (gains) losses of derivatives designated in fair value or cash flow hedging relationships: Sales Other (income) expense, net (1) Other comprehensive income (loss) Sales Other (income) expense, net (1) Other comprehensive income (loss) Three Months Ended September 30, Three Months Ended September 30, Three Months Ended September 30, Nine Months Ended September 30, Nine Months Ended September 30, Nine Months Ended September 30, ($ in millions) 2020 2019 2020 2019 2020 2019 2020 2019 2020 2019 2020 2019 Financial Statement Line Items in which Effects of Fair Value or Cash Flow Hedges are Recorded $ 12,551  $ 12,397  $ (312) $ 35  $ 10  $ (28) $ 35,479  $ 34,972  $ (630) $ 362  $ (190) $ 155  (Gain) loss on fair value hedging relationships Interest rate swap contracts Hedged items —  —  (14) 13  —  —  —  —  54  101  —  —  Derivatives designated as hedging instruments —  —  —  (6) —  —  —  —  (76) (74) —  —  Impact of cash flow hedging relationships Foreign exchange contracts Amount of (loss) gain recognized in OCI on derivatives —  —  —  —  (195) 186  —  —  —  —  (126) 183  Increase (decrease) in Sales as a result of AOCI reclassifications (23) 70  —  —  23  (70) 65  189  —  —  (65) (189) Interest rate contracts Amount of gain recognized in Other (income) expense, net on derivatives —  —  (1) (1) —  —  —  —  (3) (3) —  —  Amount of loss recognized in OCI on derivatives —  —  —  —  (1) (1) —  —  —  —  (3) (6) (1) Interest expense is a component of Other (income) expense, net. The table below provides information regarding the income statement effects of derivatives not designated as hedging instruments: Amount of Derivative Pretax (Gain) Loss Recognized in Income Three Months Ended September 30, Nine Months Ended September 30, ($ in millions) Income Statement Caption 2020 2019 2020 2019 Derivatives Not Designated as Hedging Instruments Foreign exchange contracts (1) Other (income) expense, net $ (7) $ (8) $ (138) $ 112  Foreign exchange contracts (2) Sales 7  (11) 4  (7) Interest rate contracts (3) Other (income) expense, net —  —  9  —  Forward contract related to Seagen common stock Research and development expenses 22  —  22  —  (1) These derivative contracts mitigate changes in the value of remeasured foreign currency denominated monetary assets and liabilities attributable to changes in foreign currency exchange rates. (2) These derivative contracts serve as economic hedges of forecasted transactions. (3) These derivatives serve as economic hedges against rising treasury rates. At September 30, 2020, the Company estimates $155 million of pretax net unrealized losses on derivatives maturing within the next 12 months that hedge foreign currency denominated sales over that same period will be reclassified from AOCI to Sales. The amount ultimately reclassified to Sales may differ as foreign exchange rates change. Realized gains and losses are ultimately determined by actual exchange rates at maturity. Investments in Debt and Equity Securities Information on investments in debt and equity securities is as follows:   September 30, 2020 December 31, 2019   Amortized Cost Gross Unrealized Fair Value Amortized Cost Gross Unrealized Fair Value ($ in millions) Gains Losses Gains Losses U.S. government and agency securities $ 74  $ —  $ —  $ 74  $ 266  $ 3  $ —  $ 269  Foreign government bonds 2  —  —  2  —  —  —  —  Commercial paper —  —  —  —  668  —  —  668  Corporate notes and bonds —  —  —  —  608  13  —  621  Asset-backed securities —  —  —  —  226  1  —  227  Total debt securities $ 76  $ —  $ —  $ 76  $ 1,768  $ 17  $ —  $ 1,785  Publicly traded equity securities (1) 1,477  838  Total debt and publicly traded equity securities $ 1,553  $ 2,623  (1) Unrealized net (gains) losses recognized in Other (income) expense, net on equity securities still held at September 30, 2020 were $(43) million and $(512) million in the third quarter and first nine months of 2020, respectively. Unrealized net losses (gains) recognized in Other (income) expense, net on equity securities still held at September 30, 2019 were $25 million and $(41) million in the third quarter and first nine months of 2019, respectively. At September 30, 2020 and September 30, 2019, the Company also had $508 million and $393 million, respectively, of equity investments without readily determinable fair values included in Other Assets. The Company recognizes unrealized gains on these equity investments based on favorable observable price changes from transactions involving similar investments of the same investee and recognizes unrealized losses based on unfavorable observable price changes. During the first nine months of 2020, the Company recognized unrealized gains of $21 million and unrealized losses of $3 million in Other (income) expense, net related to these equity investments held at September 30, 2020. During the first nine months of 2019, the Company recognized unrealized gains of $4 million and unrealized losses of $12 million in Other (income) expense, net related to these investments held at September 30, 2019. Cumulative unrealized gains and cumulative unrealized losses based on observable prices changes for investments in equity investments without readily determinable fair values still held at September 30, 2020 were $128 million and $24 million, respectively. Fair Value Measurements Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The Company uses a fair value hierarchy which maximizes the use of observable inputs and minimizes the use of unobservable inputs when measuring fair value. There are three levels of inputs used to measure fair value with Level 1 having the highest priority and Level 3 having the lowest: Level 1 - Quoted prices (unadjusted) in active markets for identical assets or liabilities; Level 2 - Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities; Level 3 - Unobservable inputs that are supported by little or no market activity. Level 3 assets or liabilities are those whose values are determined using pricing models, discounted cash flow methodologies, or similar techniques with significant unobservable inputs, as well as assets or liabilities for which the determination of fair value requires significant judgment or estimation. If the inputs used to measure the financial assets and liabilities fall within more than one level described above, the categorization is based on the lowest level input that is significant to the fair value measurement of the instrument. Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis Financial assets and liabilities measured at fair value on a recurring basis are summarized below: Fair Value Measurements Using Fair Value Measurements Using   Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total ($ in millions) September 30, 2020 December 31, 2019 Assets Investments Foreign government bonds $ —  $ 2  $ —  $ 2  $ —  $ —  $ —  $ —  Commercial paper —  —  —  —  —  668  —  668  Corporate notes and bonds —  —  —  —  —  621  —  621  Asset-backed securities (1) —  —  —  —  —  227  —  227  U.S. government and agency securities —  —  —  —  —  209  —  209  Publicly traded equity securities 1,370  —  —  1,370  518  —  —  518    1,370  2  —  1,372  518  1,725  —  2,243  Other assets (2) U.S. government and agency securities 74  —  —  74  60  —  —  60  Publicly traded equity securities 107  —  —  107  320  —  —  320  181  —  —  181  380  —  —  380  Derivative assets (3) Forward exchange contracts —  116  —  116  —  169  —  169  Interest rate swaps —  69  —  69  —  15  —  15  Purchased currency options —  54  —  54  —  104  —  104    —  239  —  239  —  288  —  288  Total assets $ 1,551  $ 241  $ —  $ 1,792  $ 898  $ 2,013  $ —  $ 2,911  Liabilities Other liabilities Contingent consideration $ —  $ —  $ 829  $ 829  $ —  $ —  $ 767  $ 767  Derivative liabilities (3) Forward exchange contracts —  275  —  275  —  95  —  95  Forward contract related to Seagen common stock —  22  —  22  —  —  —  —  Written currency options —  1  —  1  —  1  —  1  Interest rate swaps —  —  —  —  —  1  —  1  —  298  —  298  —  97  —  97  Total liabilities $ —  $ 298  $ 829  $ 1,127  $ —  $ 97  $ 767  $ 864  (1)Primarily all of the asset-backed securities were highly rated (Standard & Poor’s rating of AAA and Moody’s Investors Service rating of Aaa), secured primarily by auto loan, credit card and student loan receivables, with weighted-average lives of primarily 5 years or less. (2)    Investments included in other assets are restricted as to use, including for the payment of benefits under employee benefit plans. (3)    The fair value determination of derivatives includes the impact of the credit risk of counterparties to the derivatives and the Company’s own credit risk, the effects of which were not significant. As of September 30, 2020 and December 31, 2019, Cash and cash equivalents included $6.6 billion and $8.9 billion of cash equivalents, respectively (which would be considered Level 2 in the fair value hierarchy). Contingent Consideration Summarized information about the changes in liabilities for contingent consideration associated with business acquisitions is as follows: Nine Months Ended September 30, ($ in millions) 2020 2019 Fair value January 1 $ 767  $ 788  Additions 97  —  Changes in estimated fair value (1) 71  52  Payments (106) (85) Fair value September 30 (2)(3) $ 829  $ 755  (1) Recorded in Cost of sales, Research and development expenses, and Other (income) expense, net. Includes cumulative translation adjustments. (2) Balance at September 30, 2020 includes $140 million recorded as a current liability for amounts expected to be paid within the next 12 months. (3) At September 30, 2020 and December 31, 2019, $637 million and $625 million, respectively, of the liabilities relate to the termination of the Sanofi-Pasteur MSD joint venture in 2016. As part of the termination, Merck recorded a liability for contingent future royalty payments of 11.5% on net sales of all Merck products that were previously sold by the joint venture through December 31, 2024. The fair value of this liability is determined utilizing the estimated amount and timing of projected cash flows using a risk-adjusted discount rate of 8% to present value the cash flows. The additions to contingent consideration in 2020 relate to the acquisition of Themis (see Note 2). The payments of contingent consideration in both periods relate to liabilities recorded in connection with the termination of the Sanofi-Pasteur MSD joint venture in 2016. Other Fair Value Measurements Some of the Company’s financial instruments, such as cash and cash equivalents, receivables and payables, are reflected in the balance sheet at carrying value, which approximates fair value due to their short-term nature. The estimated fair value of loans payable and long-term debt (including current portion) at September 30, 2020, was $32.6 billion compared with a carrying value of $28.7 billion and at December 31, 2019, was $28.8 billion compared with a carrying value of $26.3 billion. Fair value was estimated using recent observable market prices and would be considered Level 2 in the fair value hierarchy. Concentrations of Credit Risk On an ongoing basis, the Company monitors concentrations of credit risk associated with corporate and government issuers of securities and financial institutions with which it conducts business. Credit exposure limits are established to limit a concentration with any single issuer or institution. Cash and investments are placed in instruments that meet high credit quality standards as specified in the Company’s investment policy guidelines. The majority of the Company’s accounts receivable arise from product sales in the United States, Europe and China and are primarily due from drug wholesalers and retailers, hospitals, government agencies, managed health care providers and pharmacy benefit managers. The Company monitors the financial performance and creditworthiness of its customers so that it can properly assess and respond to changes in their credit profile. The Company also continues to monitor global economic conditions, including the volatility associated with international sovereign economies, and associated impacts on the financial markets and its business. The Company has accounts receivable factoring agreements with financial institutions in certain countries to sell accounts receivable. The Company factored $2.1 billion and $2.7 billion of accounts receivable in the third quarter of 2020 and the fourth quarter of 2019, respectively, under these factoring arrangements, which reduced outstanding accounts receivable. The cash received from the financial institutions is reported within operating activities in the Consolidated Statement of Cash Flows. In certain of these factoring arrangements, for ease of administration, the Company will collect customer payments related to the factored receivables, which it then remits to the financial institutions. The net cash flows relating to these collections are reported as financing activities in the Consolidated Statement of Cash Flows. The cost of factoring such accounts receivable was de minimis. Derivative financial instruments are executed under International Swaps and Derivatives Association master agreements. The master agreements with several of the Company’s financial institution counterparties also include credit support annexes. These annexes contain provisions that require collateral to be exchanged depending on the value of the derivative assets and liabilities, the Company’s credit rating, and the credit rating of the counterparty. Cash collateral received by the Company from various counterparties was $34 million at December 31, 2019. The obligation to return such collateral is recorded in Accrued and other current liabilities. No cash collateral was advanced by the Company to counterparties as of September 30, 2020 or December 31, 2019.

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- Definition The entire disclosure for financial instruments. This disclosure includes, but is not limited to, fair value measurements of short and long term marketable securities, international currencies forward contracts, and auction rate securities. Financial instruments may include hedging and non-hedging currency exchange instruments, derivatives, securitizations and securities available for sale at fair value. Also included are investment results, realized and unrealized gains and losses as well as impairments and risk management disclosures. + References No definition available. + Details Name: us-gaap_FinancialInstrumentsDisclosureTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

v3.20.2

Inventories	9 Months Ended
	Sep. 30, 2020
Inventory Disclosure [Abstract]
Inventories	Inventories Inventories consisted of: ($ in millions) September 30, 2020 December 31, 2019 Finished goods $ 2,038  $ 1,772  Raw materials and work in process 6,073  5,650  Supplies 197  207  Total (approximates current cost) 8,308  7,629  Decrease to LIFO cost (99) (171)   $ 8,209  $ 7,458  Recognized as: Inventories $ 6,128  $ 5,978  Other assets 2,081  1,480  Amounts recognized as Other Assets are comprised almost entirely of raw materials and work in process inventories. At September 30, 2020 and December 31, 2019, these amounts included $1.8 billion and $1.3 billion, respectively, of inventories not expected to be sold within one year. In addition, these amounts included $288 million and $168 million at September 30, 2020 and December 31, 2019, respectively, of inventories produced in preparation for product launches.

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- Definition The entire disclosure for inventory. Includes, but is not limited to, the basis of stating inventory, the method of determining inventory cost, the classes of inventory, and the nature of the cost elements included in inventory. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 330 -URI http://asc.fasb.org/topic&trid=2126998 + Details Name: us-gaap_InventoryDisclosureTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

v3.20.2

Other Intangibles	9 Months Ended
	Sep. 30, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Other Intangibles	7.    Other Intangibles During the third quarter and first nine months of 2019, the Company recorded $612 million and $693 million, respectively, of intangible asset impairment charges related to marketed products within Cost of sales. During the third quarter of 2019, the Company recorded an impairment charge of $612 million related to Sivextro (tedizolid phosphate), a product for the treatment of acute bacterial skin and skin structure infections caused by susceptible isolates of certain Gram-positive microorganisms. As part of a reorganization and reprioritization of its internal sales force, the Company made the decision to cease promotion of Sivextro in the U.S. market by the end of 2019. This decision resulted in reduced cash flow projections for Sivextro, which indicated that the Sivextro intangible asset value was not fully recoverable on an undiscounted cash flows basis. The Company utilized market participant assumptions to determine its best estimate of the fair value of the intangible asset related to Sivextro that, when compared with its related carrying value, resulted in the impairment charge noted above.

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- Definition The entire disclosure for all or part of the information related to intangible assets. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -URI http://asc.fasb.org/topic&trid=2144416 + Details Name: us-gaap_IntangibleAssetsDisclosureTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

v3.20.2

Long-Term Debt	9 Months Ended
	Sep. 30, 2020
Debt Disclosure [Abstract]
Long-Term Debt	Long-Term DebtIn June 2020, the Company issued $4.5 billion principal amount of senior unsecured notes consisting of $1.0 billion of 0.75% notes due 2026, $1.25 billion of 1.45% notes due 2030, $1.0 billion of 2.35% notes due 2040 and $1.25 billion of 2.45% notes due 2050. Merck used the net proceeds from the offering for general corporate purposes, including without limitation the repayment of outstanding commercial paper borrowings and other indebtedness with upcoming maturities.

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- Definition The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -URI http://asc.fasb.org/topic&trid=2208564 + Details Name: us-gaap_DebtDisclosureTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

v3.20.2

Contingencies	9 Months Ended
	Sep. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
Contingencies	Contingencies The Company is involved in various claims and legal proceedings of a nature considered normal to its business, including product liability, intellectual property, and commercial litigation, as well as certain additional matters including governmental and environmental matters. In the opinion of the Company, it is unlikely that the resolution of these matters will be material to the Company’s financial condition, results of operations or cash flows. Given the nature of the litigation discussed below and the complexities involved in these matters, the Company is unable to reasonably estimate a possible loss or range of possible loss for such matters until the Company knows, among other factors, (i) what claims, if any, will survive dispositive motion practice, (ii) the extent of the claims, including the size of any potential class, particularly when damages are not specified or are indeterminate, (iii) how the discovery process will affect the litigation, (iv) the settlement posture of the other parties to the litigation and (v) any other factors that may have a material effect on the litigation. The Company records accruals for contingencies when it is probable that a liability has been incurred and the amount can be reasonably estimated. These accruals are adjusted periodically as assessments change or additional information becomes available. For product liability claims, a portion of the overall accrual is actuarially determined and considers such factors as past experience, number of claims reported and estimates of claims incurred but not yet reported. Individually significant contingent losses are accrued when probable and reasonably estimable. Legal defense costs expected to be incurred in connection with a loss contingency are accrued when probable and reasonably estimable. The Company’s decision to obtain insurance coverage is dependent on market conditions, including cost and availability, existing at the time such decisions are made. The Company has evaluated its risks and has determined that the cost of obtaining product liability insurance outweighs the likely benefits of the coverage that is available and, as such, has no insurance for most product liabilities. Product Liability Litigation Fosamax As previously disclosed, Merck is a defendant in product liability lawsuits in the United States involving Fosamax (Fosamax Litigation). As of September 30, 2020, approximately 3,590 cases are pending against Merck in either federal or state court. Plaintiffs in the vast majority of these cases generally allege that they sustained femur fractures and/or other bone injuries (Femur Fractures) in association with the use of Fosamax. All federal cases involving allegations of Femur Fractures have been or will be transferred to a multidistrict litigation in the District of New Jersey (Femur Fracture MDL). In the only bellwether case tried to date in the Femur Fracture MDL, Glynn v. Merck, the jury returned a verdict in Merck’s favor. In addition, in June 2013, the Femur Fracture MDL court granted Merck’s motion for judgment as a matter of law in the Glynn case and held that the plaintiff’s failure to warn claim was preempted by federal law. In August 2013, the Femur Fracture MDL court entered an order requiring plaintiffs in the Femur Fracture MDL to show cause why those cases asserting claims for a femur fracture injury that took place prior to September 14, 2010, should not be dismissed based on the court’s preemption decision in the Glynn case. Pursuant to the show cause order, in March 2014, the Femur Fracture MDL court dismissed with prejudice approximately 650 cases on preemption grounds. Plaintiffs in approximately 515 of those cases appealed that decision to the U.S. Court of Appeals for the Third Circuit (Third Circuit). In March 2017, the Third Circuit issued a decision reversing the Femur Fracture MDL court’s preemption ruling and remanding the appealed cases back to the Femur Fracture MDL court. In May 2019, the U.S. Supreme Court decided that the Third Circuit had incorrectly concluded that the issue of preemption should be resolved by a jury, and accordingly vacated the judgment of the Third Circuit and remanded the proceedings back to the Third Circuit to address the issue in a manner consistent with the Supreme Court’s opinion. In November 2019, the Third Circuit remanded the cases back to the District Court in order to allow that court to determine in the first instance whether the plaintiffs’ state law claims are preempted by federal law under the standards described by the Supreme Court in its opinion. Briefing on the issue is closed, and the parties await the decision of the District Court. Accordingly, as of September 30, 2020, approximately 970 cases were actively pending in the Femur Fracture MDL. As of September 30, 2020, approximately 2,340 cases alleging Femur Fractures have been filed in New Jersey state court and are pending before Judge James Hyland in Middlesex County. The parties selected an initial group of cases to be reviewed through fact discovery, and Merck has continued to select additional cases to be reviewed. As of September 30, 2020, approximately 275 cases alleging Femur Fractures have been filed and are pending in California state court. All of the Femur Fracture cases filed in California state court have been coordinated before a single judge in Orange County, California. Additionally, there are four Femur Fracture cases pending in other state courts. Discovery is presently stayed in the Femur Fracture MDL and in the state court in California. Merck intends to defend against these lawsuits. Januvia/Janumet As previously disclosed, Merck is a defendant in product liability lawsuits in the United States involving Januvia and/or Janumet. As of September 30, 2020, Merck is aware of approximately 1,465 product users alleging that Januvia and/or Janumet caused the development of pancreatic cancer and other injuries. Most claims have been filed in multidistrict litigation before the U.S. District Court for the Southern District of California (MDL). Outside of the MDL, the majority of claims have been filed in coordinated proceedings before the Superior Court of California, County of Los Angeles (California State Court). In November 2015, the MDL and California State Court–in separate opinions–granted summary judgment to defendants on grounds of federal preemption. Plaintiffs appealed in both forums. In November 2017, the U.S. Court of Appeals for the Ninth Circuit vacated the judgment and remanded for further discovery. In November 2018, the California state appellate court reversed and remanded on similar grounds. In March 2019, the parties in the MDL and the California coordinated proceedings agreed to coordinate and adopt a schedule for completing discovery on general causation and preemption issues and for renewing summary judgment and Daubert motions. Under the stipulated case management schedule, the hearings for Daubert and summary judgment motions took place on October 20, 2020. As of September 30, 2020, six product users have claims pending against Merck in state courts other than California, including Illinois. In June 2017, the Illinois trial court denied Merck’s motion for summary judgment based on federal preemption. Merck appealed, and the Illinois appellate court affirmed in December 2018. Merck filed a petition for leave to appeal to the Illinois Supreme Court in February 2019. In April 2019, the Illinois Supreme Court stayed consideration of the pending petition to appeal until the U.S. Supreme Court issued its opinion in Merck Sharp & Dohme Corp. v. Albrecht (relating to the Fosamax matter discussed above). Merck filed the opinion in Albrecht with the Illinois Supreme Court in June 2019. The petition for leave to appeal was decided in September 2019, in which the Illinois Supreme Court directed the intermediate appellate court to reconsider its earlier ruling. The Illinois Appellate Court issued a favorable decision concluding, consistent with Albrecht, that preemption presents a legal question to be resolved by the court. In addition to the claims noted above, the Company has agreed to toll the statute of limitations for approximately 50 additional claims. The Company intends to continue defending against these lawsuits. Vioxx As previously disclosed, Merck is a defendant in a lawsuit brought by the Attorney General of Utah alleging that Merck misrepresented the safety of Vioxx. The lawsuit is pending in Utah state court. Utah seeks damages and penalties under the Utah False Claims Act. A bench trial in this matter has been rescheduled for April 6, 2021. Governmental Proceedings As previously disclosed, the Company’s subsidiaries in China have received and may continue to receive inquiries regarding their operations from various Chinese governmental agencies. Some of these inquiries may be related to matters involving other multinational pharmaceutical companies, as well as Chinese entities doing business with such companies. The Company’s policy is to cooperate with these authorities and to provide responses as appropriate. As previously disclosed, from time to time, the Company receives inquiries and is the subject of preliminary investigation activities from competition and other governmental authorities in markets outside the United States. These authorities may include regulators, administrative authorities, and law enforcement and other similar officials, and these preliminary investigation activities may include site visits, formal or informal requests or demands for documents or materials, inquiries or interviews and similar matters. Certain of these preliminary inquiries or activities may lead to the commencement of formal proceedings. Should those proceedings be determined adversely to the Company, monetary fines and/or remedial undertakings may be required. Commercial and Other Litigation Zetia Antitrust Litigation As previously disclosed, Merck, MSD, Schering Corporation and MSP Singapore Company LLC (collectively, the Merck Defendants) are defendants in putative class action and opt-out lawsuits filed in 2018 on behalf of direct and indirect purchasers of Zetia alleging violations of federal and state antitrust laws, as well as other state statutory and common law causes of action. The cases have been consolidated for pretrial purposes in a federal multidistrict litigation before Judge Rebecca Beach Smith in the Eastern District of Virginia. In December 2018, the court denied the Merck Defendants’ motions to dismiss or stay the direct purchaser putative class actions pending bilateral arbitration. In August 2019, the district court adopted in full the report and recommendation of the magistrate judge with respect to the Merck Defendants’ motions to dismiss on non-arbitration issues, thereby granting in part and denying in part Merck Defendants’ motions to dismiss. In addition, in June 2019, the representatives of the putative direct purchaser class filed an amended complaint, and in August 2019, retailer opt-out plaintiffs filed an amended complaint. The Merck Defendants moved to dismiss the new allegations in both complaints. In October 2019, the magistrate judge issued a report and recommendation recommending that the district judge grant the motions in their entirety. In December 2019, the district court adopted this report and recommendation in part. The district court granted the Merck Defendants’ motion to dismiss to the extent the motion sought dismissal of claims for overcharges paid by entities that purchased generic ezetimibe from Par Pharmaceutical, Inc. (Par Pharmaceutical) and dismissed any claims for such overcharges. In November 2019, the direct purchaser plaintiffs and the indirect purchaser plaintiffs filed motions for class certification. On June 18, 2020, the magistrate judge issued a report and recommendation recommending that the district judge grant in part the direct purchasers’ motion for class certification and certify a class of 35 direct purchasers. On August 21, 2020, the district court adopted the report and recommendation in full, and on November 2, 2020, the U.S. Court of Appeals for the Fourth Circuit granted defendants’ motion for permission to appeal the district court’s order. Also, on August 14, 2020, the magistrate judge recommended that the court grant the motion for class certification filed by the putative indirect purchaser class. The Merck Defendants objected to this report and recommendation and are awaiting a decision from the district court. On August 10, 2020, the Merck Defendants filed a motion for summary judgment and other motions, and plaintiffs filed a motion for partial summary judgment, and other motions. Those motions are now fully briefed, and the court will likely hold a hearing on the competing motions. Trial in this matter has been adjourned. Patent Litigation From time to time, generic manufacturers of pharmaceutical products file abbreviated New Drug Applications (NDAs) with the FDA seeking to market generic forms of the Company’s products prior to the expiration of relevant patents owned by the Company. To protect its patent rights, the Company may file patent infringement lawsuits against such generic companies. Similar lawsuits defending the Company’s patent rights may exist in other countries. The Company intends to vigorously defend its patents, which it believes are valid, against infringement by companies attempting to market products prior to the expiration of such patents. As with any litigation, there can be no assurance of the outcomes, which, if adverse, could result in significantly shortened periods of exclusivity for these products and, with respect to products acquired through acquisitions, potentially significant intangible asset impairment charges. Bridion — Between January and March 2020, the Company received multiple Paragraph IV Certification Letters under the Hatch-Waxman Act notifying the Company that generic drug companies have filed applications to the FDA seeking pre-patent expiry approval to sell generic versions of Bridion (sugammadex) Injection. In March and April 2020, the Company filed patent infringement lawsuits in the U.S. District Courts for the District of New Jersey and the Northern District of West Virginia against those generic companies. These lawsuits, which assert one or more patents covering sugammadex and methods of using sugammadex, automatically stay FDA approval of the generic applications until June 2023 or until adverse court decisions, if any, whichever may occur earlier. Mylan Pharmaceuticals Inc., Mylan API US LLC, and Mylan Inc. (Mylan) have filed motions to dismiss in the District of New Jersey for lack of venue and failure to state a claim against certain defendants, and in the Northern District of West Virginia for failure to state a claim against certain defendants. The New Jersey motion has not yet been decided, and the West Virginia action is stayed pending resolution of the New Jersey motion. All New Jersey actions against all defendants have been consolidated. Januvia, Janumet, Janumet XR — In February 2019, Par Pharmaceutical filed suit against the Company in the U.S. District Court for the District of New Jersey, seeking a declaratory judgment of invalidity of a patent owned by the Company covering certain salt and polymorphic forms of sitagliptin that expires in 2026. In response, the Company filed a patent infringement lawsuit in the U.S. District Court for the District of Delaware against Par Pharmaceutical and additional companies that also indicated an intent to market generic versions of Januvia, Janumet, and Janumet XR following expiration of key patent protection in 2022, but prior to the expiration of the later-granted patent owned by the Company covering certain salt and polymorphic forms of sitagliptin that expires in 2026 (2026 salt/polymorph patent), and a later granted patent owned by the Company covering the Janumet formulation which expires in 2028. Par Pharmaceutical dismissed its case in the U.S. District Court for the District of New Jersey against the Company and will litigate the action in the U.S. District Court for the District of Delaware. The Company filed a patent infringement lawsuit against Mylan in the Northern District of West Virginia. The Judicial Panel of Multidistrict Litigation entered an order transferring the Company’s lawsuit against Mylan to the U.S. District Court for the District of Delaware for coordinated and consolidated pretrial proceedings with the other cases pending in that district. The U.S. District Court for the District of Delaware has scheduled the lawsuits for a single three-day trial on invalidity issues in October 2021. The Court will schedule separate one-day trials on infringement issues if necessary. In the Company’s case against Mylan, the U.S. District Court for the Northern District of West Virginia has conditionally scheduled a three-day trial in December 2021 on all issues. In February 2020, the Company amended its complaint against one defendant, Teva Pharmaceuticals USA, Inc., to add patent infringement claims related to a patent that expires in 2025 and covers certain processes for manufacturing sitagliptin. In July 2020, the Company amended its complaints against two defendants, Teva Pharmaceuticals USA, Inc. and Watson Laboratories, Inc., to add patent infringement claims related to a patent that also expires in 2026 and covers certain amorphous forms of sitagliptin. The Company has settled with five generic companies such that these generic companies can bring their products to the market in November 2026 or earlier under certain circumstances. In October 2019, Mylan filed a petition for Inter Partes Review (IPR) at the United States Patent and Trademark Office (USPTO) seeking invalidity of some, but not all, of the claims of the 2026 salt/polymorph patent. The USPTO instituted IPR proceedings in May 2020, finding a reasonable likelihood that the challenged claims are not valid. A trial is scheduled for February 2021 and a final decision is expected in May 2021. After institution, three additional IPR petitions were filed by Teva Pharmaceuticals USA, Inc., Dr. Reddy’s Laboratories, Inc., and Sun Pharmaceutical Industries Ltd., as well as related entities, which requested joinder with Mylan’s IPR proceedings. If the challenges are successful, the unchallenged claims of the 2026 salt/polymorph patent will remain valid, subject to the court proceedings described above. In Germany, two generic companies have sought the revocation of the Supplementary Protection Certificate (SPC) for Janumet. If the generic companies are successful, Janumet could lose market exclusivity in Germany as early as July 2022. Challenges to the Janumet SPC have also occurred in Portugal and Finland, and could occur in other European countries. Other Litigation There are various other pending legal proceedings involving the Company, principally product liability and intellectual property lawsuits. While it is not feasible to predict the outcome of such proceedings, in the opinion of the Company, either the likelihood of loss is remote or any reasonably possible loss associated with the resolution of such proceedings is not expected to be material to the Company’s financial condition, results of operations or cash flows either individually or in the aggregate. Legal Defense Reserves Legal defense costs expected to be incurred in connection with a loss contingency are accrued when probable and reasonably estimable. Some of the significant factors considered in the review of these legal defense reserves are as follows: the actual costs incurred by the Company; the development of the Company’s legal defense strategy and structure in light of the scope of its litigation; the number of cases being brought against the Company; the costs and outcomes of completed trials and the most current information regarding anticipated timing, progression, and related costs of pre-trial activities and trials in the associated litigation. The amount of legal defense reserves as of September 30, 2020 and December 31, 2019 of approximately $255 million and $240 million, respectively, represents the Company’s best estimate of the minimum amount of defense costs to be incurred in connection with its outstanding litigation; however, events such as additional trials and other events that could arise in the course of its litigation could affect the ultimate amount of legal defense costs to be incurred by the Company. The Company will continue to monitor its legal defense costs and review the adequacy of the associated reserves and may determine to increase the reserves at any time in the future if, based upon the factors set forth, it believes it would be appropriate to do so.

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- Definition The entire disclosure for commitments and contingencies. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -URI http://asc.fasb.org/topic&trid=2127136 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 440 -URI http://asc.fasb.org/topic&trid=2144648 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 440 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=121559207&loc=d3e25336-109308 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 440 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121559207&loc=d3e25336-109308 + Details Name: us-gaap_CommitmentsAndContingenciesDisclosureTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

v3.20.2

Equity	9 Months Ended
	Sep. 30, 2020
Equity [Abstract]
Equity	Equity Three Months Ended September 30,      Common Stock Other Paid-In Capital Retained Earnings Accumulated Other Comprehensive Loss   Treasury Stock Non- controlling Interests Total ($ and shares in millions except per share amounts) Shares Par Value Shares Cost Balance at July 1, 2019 3,577  $ 1,788  $ 39,484  $ 45,295  $ (5,362) 1,010  $ (53,570) $ 102  $ 27,737  Net income attributable to Merck & Co., Inc. —  —  —  1,901  —  —  —  —  1,901  Other comprehensive loss, net of taxes —  —  —  —  (28) —  —  —  (28) Cash dividends declared on common stock ($0.55 per share) —  —  —  (1,392) —  —  —  —  (1,392) Treasury stock shares purchased —  —  —  —  —  17  (1,405) —  (1,405) Share-based compensation plans and other —  —  77  —  —  (1) 50  —  127  Net income attributable to noncontrolling interests —  —  —  —  —  —  —  6  6  Distributions attributable to noncontrolling interests —  —  —  —  —  —  —  (21) (21) Balance at September 30, 2019 3,577  $ 1,788  $ 39,561  $ 45,804  $ (5,390) 1,026  $ (54,925) $ 87  $ 26,925  Balance at July 1, 2020 3,577  $ 1,788  $ 39,373  $ 49,724  $ (6,393) 1,048  $ (56,850) $ 102  $ 27,744  Net income attributable to Merck & Co., Inc. —  —  —  2,941  —  —  —  —  2,941  Other comprehensive income, net of taxes —  —  —  —  10  —  —  —  10  Cash dividends declared on common stock ($0.61 per share) —  —  —  (1,558) —  —  —  —  (1,558) Share-based compensation plans and other —  —  116  —  —  (1) 35  —  151  Net income attributable to noncontrolling interests —  —  —  —  —  —  —  4  4  Distributions attributable to noncontrolling interests —  —  —  —  —  —  —  (22) (22) Balance at September 30, 2020 3,577  $ 1,788  $ 39,489  $ 51,107  $ (6,383) 1,047  $ (56,815) $ 84  $ 29,270  Nine Months Ended September 30,      Common Stock Other Paid-In Capital Retained Earnings Accumulated Other Comprehensive Loss   Treasury Stock Non- controlling Interests Total ($ and shares in millions except per share amounts) Shares Par Value Shares Cost Balance at January 1, 2019 3,577  $ 1,788  $ 38,808  $ 42,579  $ (5,545) 985  $ (50,929) $ 181  $ 26,882  Net income attributable to Merck & Co., Inc. —  —  —  7,487  —  —  —  —  7,487  Other comprehensive income, net of taxes —  —  —  —  155  —  —  —  155  Cash dividends declared on common stock ($1.65 per share) —  —  —  (4,262) —  —  —  —  (4,262) Treasury stock shares purchased —  —  1,000  —  —  54  (4,730) —  (3,730) Share-based compensation plans and other —  —  (247) —  —  (13) 734  —  487  Net loss attributable to noncontrolling interests —  —  —  —  —  —  —  (73) (73) Distributions attributable to noncontrolling  interests —  —  —  —  —  —  —  (21) (21) Balance at September 30, 2019 3,577  1,788  39,561  45,804  (5,390) 1,026  (54,925) 87  26,925  Balance at January 1, 2020 3,577  $ 1,788  $ 39,660  $ 46,602  $ (6,193) 1,038  $ (55,950) $ 94  $ 26,001  Net income attributable to Merck & Co., Inc. —  —  —  9,161  —  —  —  —  9,161  Other comprehensive loss, net of taxes —  —  —  —  (190) —  —  —  (190) Cash dividends declared on common stock ($1.83 per share) —  —  —  (4,656) —  —  —  —  (4,656) Treasury stock shares purchased —  —  —  —  —  16  (1,281) —  (1,281) Share-based compensation plans and other —  —  (171) —  —  (7) 416  —  245  Net income attributable to noncontrolling interests —  —  —  —  —  —  —  12  12  Distributions attributable to noncontrolling  interests —  —  —  —  —  —  —  (22) (22) Balance at September 30, 2020 3,577  $ 1,788  $ 39,489  $ 51,107  $ (6,383) 1,047  $ (56,815) $ 84  $ 29,270

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- Definition The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08(e)(1)) -URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=120397183&loc=d3e187085-122770 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -URI http://asc.fasb.org/topic&trid=2208762 + Details Name: us-gaap_StockholdersEquityNoteDisclosureTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

v3.20.2

Share-Based Compensation Plans	9 Months Ended
	Sep. 30, 2020
Share-based Payment Arrangement [Abstract]
Share-Based Compensation Plans	Share-Based Compensation Plans The Company has share-based compensation plans under which the Company grants restricted stock units (RSUs) and performance share units (PSUs) to certain management level employees. In addition, employees and non-employee directors may be granted options to purchase shares of Company common stock at the fair market value at the time of grant. The following table provides the amounts of share-based compensation cost recorded in the Condensed Consolidated Statement of Income:   Three Months Ended September 30, Nine Months Ended September 30, ($ in millions) 2020 2019 2020 2019 Pretax share-based compensation expense $ 126  $ 101  $ 354  $ 306  Income tax benefit (17) (14) (48) (42) Total share-based compensation expense, net of taxes $ 109  $ 87  $ 306  $ 264  During the first nine months of 2020, the Company granted 7 million RSUs with a weighted-average grant date fair value of $77.83 per RSU and during the first nine months of 2019 granted 5 million RSUs with a weighted-average grant date fair value of $80.03 per RSU. During the first nine months of 2020, the Company granted 773 thousand PSUs with a weighted-average grant date fair value of $75.22 per PSU and during the first nine months of 2019 granted 609 thousand PSUs with a weighted-average grant date fair value of $90.50 per PSU. During the first nine months of 2020, the Company granted 4 million stock options with a weighted-average exercise price of $77.67 per option and during the first nine months of 2019 granted 3 million stock options with a weighted-average exercise price of $80.05 per option. The weighted-average fair value of options granted during the first nine months of 2020 and 2019 was $9.93 and $10.63 per option, respectively, and was determined using the following assumptions:    Nine Months Ended September 30, 2020 2019 Expected dividend yield 3.1  % 3.2  % Risk-free interest rate 0.4  % 2.4  % Expected volatility 22.1  % 18.7  % Expected life (years) 5.8 5.9 At September 30, 2020, there was $800 million of total pretax unrecognized compensation expense related to nonvested stock options, RSU and PSU awards which will be recognized over a weighted-average period of 2.1 years. For segment reporting, share-based compensation costs are unallocated expenses.

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- Definition The entire disclosure for share-based payment arrangement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -URI http://asc.fasb.org/topic&trid=2228938 + Details Name: us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

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v3.20.2

Pension and Other Postretirement Benefit Plans	9 Months Ended
	Sep. 30, 2020
Retirement Benefits [Abstract]
Pension and Other Postretirement Benefit Plans	Pension and Other Postretirement Benefit Plans The Company has defined benefit pension plans covering eligible employees in the United States and in certain of its international subsidiaries. The net periodic benefit cost of such plans consisted of the following components:     Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 ($ in millions) U.S. International U.S. International U.S. International U.S. International Service cost $ 96  $ 77  $ 76  $ 58  $ 270  $ 225  $ 221  $ 178  Interest cost 107  35  115  44  323  103  343  133  Expected return on plan assets (193) (104) (202) (106) (581) (310) (613) (320) Amortization of unrecognized prior service credit (12) (3) (12) (3) (37) (9) (37) (9) Net loss amortization 75  32  43  16  228  94  113  47  Termination benefits 1  1  3  —  5  2  7  1  Curtailments 1  —  5  —  4  (1) 6  —  Settlements 2  —  —  —  11  2  —  —    $ 77  $ 38  $ 28  $ 9  $ 223  $ 106  $ 40  $ 30  The Company anticipates that in 2020 it will contribute approximately $200 million and $375 million to its U.S. and international pension plans, respectively, of which $184 million and $123 million, respectively, was contributed in the first nine months of the year. The Company provides medical benefits, principally to its eligible U.S. retirees and similar benefits to their dependents, through its other postretirement benefit plans. The net credit of such plans consisted of the following components:     Three Months Ended September 30, Nine Months Ended September 30, ($ in millions) 2020 2019 2020 2019 Service cost $ 13  $ 12  $ 39  $ 36  Interest cost 14  17  43  52  Expected return on plan assets (19) (18) (56) (54) Amortization of unrecognized prior service credit (18) (20) (54) (59) Net gain amortization (5) (3) (13) (7) Termination benefits —  1  —  1  Curtailments —  (3) (1) (4)   $ (15) $ (14) $ (42) $ (35) In connection with restructuring actions (see Note 4), termination charges were recorded on pension plans related to expanded eligibility for certain employees exiting Merck. Also, in connection with these restructuring actions, curtailments were recorded on pension and other postretirement benefit plans and settlements were recorded on certain U.S. and international pension plans as reflected in the tables above. The components of net periodic benefit cost (credit) other than the service cost component are included in Other (income) expense, net (see Note 13), with the exception of certain amounts for termination benefits, curtailments and settlements, which are recorded in Restructuring costs if the event giving rise to the termination benefits, curtailment or settlement is related to restructuring actions as noted above.

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- Definition The entire disclosure for retirement benefits. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4179-114921 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section S99 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=21916913&loc=d3e273930-122802 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(i) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (o) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (p) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -URI http://asc.fasb.org/topic&trid=2235017 Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 60 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6414203&loc=d3e39689-114964 Reference 9: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(03) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 10: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (q) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 11: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (r)(1) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 12: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(iii) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 13: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (l) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 14: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (r)(2) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details Name: us-gaap_PensionAndOtherPostretirementBenefitsDisclosureTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

v3.20.2

Other (Income) Expense, Net	9 Months Ended
	Sep. 30, 2020
Other Income and Expenses [Abstract]
Other (Income) Expense, Net	Other (Income) Expense, Net Other (income) expense, net, consisted of:    Three Months Ended September 30, Nine Months Ended September 30, ($ in millions) 2020 2019 2020 2019 Interest income $ (9) $ (61) $ (48) $ (225) Interest expense 203  231  624  674  Exchange losses 10  38  89  166  Income from investments in equity securities, net (1) (360) (16) (964) (50) Net periodic defined benefit plan (credit) cost other than service cost (88) (128) (259) (409) Other, net (68) (29) (72) 206    $ (312) $ 35  $ (630) $ 362  (1)    Includes net realized and unrealized gains and losses from investments in equity securities either owned directly or through ownership interests in investment funds. Unrealized gains and losses from investments that are directly owned are determined at the end of the reporting period, while ownership interests in investment funds are accounted for on a one quarter lag. The decline in interest income in the third quarter and first nine months of 2020 reflects lower investments and lower interest rates. The lower exchange losses in the first nine months of 2020 reflect losses on forward exchange contracts in 2019 related to the acquisition of Antelliq. The increase in income from investments in equity securities, net, in both the third quarter and first nine months of 2020 was driven primarily by the recognition of unrealized gains on certain investments, most of which relate to Moderna, Inc. Other, net (as reflected in the table above) in the first nine months of 2019 includes $162 million of goodwill impairment charges related to certain businesses in the Healthcare Services segment. Interest paid for the nine months ended September 30, 2020 and 2019 was $605 million and $629 million, respectively.

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- References No definition available. + Details Name: us-gaap_OtherIncomeAndExpensesAbstract Namespace Prefix: us-gaap_ Data Type: xbrli:stringItemType Balance Type: na Period Type: duration

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- Definition The entire disclosure for other income or other expense items (both operating and nonoperating). Sources of nonoperating income or nonoperating expense that may be disclosed, include amounts earned from dividends, interest on securities, profits (losses) on securities, net and miscellaneous other income or income deductions. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 720 -URI http://asc.fasb.org/topic&trid=2122503 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 610 -URI http://asc.fasb.org/topic&trid=49130413 + Details Name: us-gaap_OtherIncomeAndOtherExpenseDisclosureTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

v3.20.2

Taxes on Income	9 Months Ended
	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Taxes on Income	Taxes on Income The effective income tax rates of 14.1% and 18.7% for the third quarter of 2020 and 2019, respectively, and 14.9% and 14.5% for the first nine months of 2020 and 2019, respectively, reflect the impacts of acquisition and divestiture-related costs and restructuring costs, partially offset by the beneficial impact of foreign earnings. The effective income tax rates in the third quarter and first nine months of 2019 also reflect the unfavorable impact of a charge for the acquisition of Peloton for which no tax benefit was recognized and the favorable impact of product mix on the estimated 2019 full-year tax rate. In addition, the effective income tax rate for the first nine months of 2019 reflects the favorable impact of a $360 million net tax benefit related to the settlement of certain federal income tax matters. In the first quarter of 2019, the Internal Revenue Service (IRS) concluded its examinations of Merck’s 2012-2014 U.S. federal income tax returns. As a result, the Company was required to make a payment of $107 million. The Company’s reserves for unrecognized tax benefits for the years under examination exceeded the adjustments relating to this examination period and therefore the Company recorded a $360 million net tax benefit in the first nine months of 2019. This net benefit reflects reductions in reserves for unrecognized tax benefits for tax positions relating to the years that were under examination, partially offset by additional reserves for tax positions not previously reserved for.

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- References No definition available. + Details Name: us-gaap_IncomeTaxDisclosureAbstract Namespace Prefix: us-gaap_ Data Type: xbrli:stringItemType Balance Type: na Period Type: duration

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- Definition The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 21 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32857-109319 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SAB Topic 11.C) -URI http://asc.fasb.org/extlink&oid=116825942&loc=d3e330215-122817 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 17 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32809-109319 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 6.I.5.Q1) -URI http://asc.fasb.org/extlink&oid=116825942&loc=d3e330036-122817 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 14 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32705-109319 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 270 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6424409&loc=d3e44925-109338 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -URI http://asc.fasb.org/topic&trid=2144680 Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6424122&loc=d3e41874-109331 + Details Name: us-gaap_IncomeTaxDisclosureTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

v3.20.2

Earnings Per Share	9 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
Earnings Per Share	Earnings Per Share The calculations of earnings per share are as follows:   Three Months Ended September 30, Nine Months Ended September 30, ($ and shares in millions except per share amounts) 2020 2019 2020 2019 Net income attributable to Merck & Co., Inc. $ 2,941  $ 1,901  $ 9,161  $ 7,487  Average common shares outstanding 2,529  2,558  2,530  2,572  Common shares issuable (1) 9  14  11  15  Average common shares outstanding assuming dilution 2,538  2,572  2,541  2,587  Basic earnings per common share attributable to Merck & Co., Inc. common shareholders $ 1.16  $ 0.74  $ 3.62  $ 2.91  Earnings per common share assuming dilution attributable to Merck & Co., Inc. common shareholders $ 1.16  $ 0.74  $ 3.61  $ 2.89  (1)Issuable primarily under share-based compensation plans. For the third quarter of 2020 and 2019, 5 million and 3 million, respectively, and for the first nine months of 2020 and 2019, 5 million and 2 million, respectively, of common shares issuable under share-based compensation plans were excluded from the computation of earnings per common share assuming dilution because the effect would have been antidilutive.

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- References No definition available. + Details Name: us-gaap_EarningsPerShareAbstract Namespace Prefix: us-gaap_ Data Type: xbrli:stringItemType Balance Type: na Period Type: duration

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- Definition The entire disclosure for earnings per share. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=109243012&loc=SL65017193-207537 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -URI http://asc.fasb.org/topic&trid=2144383 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3630-109257 + Details Name: us-gaap_EarningsPerShareTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

v3.20.2

Other Comprehensive Income (Loss)	9 Months Ended
	Sep. 30, 2020
Equity [Abstract]
Other Comprehensive Income (Loss)	Other Comprehensive Income (Loss) Changes in AOCI by component are as follows: Three Months Ended September 30, ($ in millions) Derivatives Investments Employee Benefit Plans Cumulative Translation Adjustment Accumulated Other Comprehensive Income (Loss) Balance July 1, 2019, net of taxes $ 66  $ 48  $ (3,530) $ (1,946) $ (5,362) Other comprehensive income (loss) before reclassification adjustments, pretax 186  8  (4) (84) 106  Tax (39) —  —  (33) (72) Other comprehensive income (loss) before reclassification adjustments, net of taxes 147  8  (4) (117) 34  Reclassification adjustments, pretax (71) (1) (25) (2) 21  (3) —  (75) Tax 15  —  (2) —  13  Reclassification adjustments, net of taxes (56) (25) 19  —  (62) Other comprehensive income (loss), net of taxes 91  (17) 15  (117) (28) Balance September 30, 2019, net of taxes $ 157  $ 31  $ (3,515) $ (2,063) $ (5,390) Balance July 1, 2020, net of taxes $ 15  $ —  $ (4,162) $ (2,246) $ (6,393) Other comprehensive income (loss) before reclassification adjustments, pretax (195) —  2  50  (143) Tax 41  —  1  35  77  Other comprehensive income (loss) before reclassification adjustments, net of taxes (154) —  3  85  (66) Reclassification adjustments, pretax 22  (1) —  72  (3) —  94  Tax (5) —  (13) —  (18) Reclassification adjustments, net of taxes 17  —  59  —  76  Other comprehensive income (loss), net of taxes (137) —  62  85  10  Balance September 30, 2020, net of taxes $ (122) $ —  $ (4,100) $ (2,161) $ (6,383) Nine Months Ended September 30, ($ in millions) Derivatives Investments Employee Benefit Plans Cumulative Translation Adjustment Accumulated Other Comprehensive Income (Loss) Balance January 1, 2019, net of taxes $ 166  $ (78) $ (3,556) $ (2,077) $ (5,545) Other comprehensive income (loss) before reclassification adjustments, pretax 183  139  (5) 47  364  Tax (38) —  6  (33) (65) Other comprehensive income (loss) before reclassification adjustments, net of taxes 145  139  1  14  299  Reclassification adjustments, pretax (195) (1) (30) (2) 49  (3) —  (176) Tax 41  —  (9) —  32  Reclassification adjustments, net of taxes (154) (30) 40  —  (144) Other comprehensive income (loss), net of taxes (9) 109  41  14  155  Balance September 30, 2019, net of taxes $ 157  $ 31  $ (3,515) $ (2,063) $ (5,390) Balance January 1, 2020, net of taxes $ 31  $ 18  $ (4,261) $ (1,981) $ (6,193) Other comprehensive income (loss) before reclassification adjustments, pretax (126) 3  (19) (220) (362) Tax 27  —  12  40  79  Other comprehensive income (loss) before reclassification adjustments, net of taxes (99) 3  (7) (180) (283) Reclassification adjustments, pretax (68) (1) (21) (2) 210  (3) —  121  Tax 14  —  (42) —  (28) Reclassification adjustments, net of taxes (54) (21) 168  —  93  Other comprehensive income (loss), net of taxes (153) (18) 161  (180) (190) Balance September 30, 2020, net of taxes $ (122) $ —  $ (4,100) $ (2,161) $ (6,383) (1) Relates to foreign currency cash flow hedges that were reclassified from AOCI to Sales. (2) Represents net realized (gains) losses on the sales of available-for-sale debt securities that were reclassified from AOCI to Other (income) expense, net. (3) Includes net amortization of prior service cost and actuarial gains and losses included in net periodic benefit cost (see Note 12).

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- Definition The entire disclosure for comprehensive income, which includes, but is not limited to, 1) the amount of income tax expense or benefit allocated to each component of other comprehensive income, including reclassification adjustments, 2) the reclassification adjustments for each classification of other comprehensive income and 3) the ending accumulated balances for each component of comprehensive income. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -URI http://asc.fasb.org/topic&trid=2134417 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03(21)) -URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04(23)) -URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(19)) -URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263 + Details Name: us-gaap_ComprehensiveIncomeNoteTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

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- References No definition available. + Details Name: us-gaap_EquityAbstract Namespace Prefix: us-gaap_ Data Type: xbrli:stringItemType Balance Type: na Period Type: duration

v3.20.2

Segment Reporting	9 Months Ended
	Sep. 30, 2020
Segment Reporting [Abstract]
Segment Reporting	Segment Reporting The Company’s operations are principally managed on a products basis and include three operating segments, which are the Pharmaceutical, Animal Health and Healthcare Services segments. The Pharmaceutical and Animal Health segments are the only reportable segments. The Pharmaceutical segment includes human health pharmaceutical and vaccine products. Human health pharmaceutical products consist of therapeutic and preventive agents, generally sold by prescription, for the treatment of human disorders. The Company sells these human health pharmaceutical products primarily to drug wholesalers and retailers, hospitals, government agencies and managed health care providers such as health maintenance organizations, pharmacy benefit managers and other institutions. Human health vaccine products consist of preventive pediatric, adolescent and adult vaccines, primarily administered at physician offices. The Company sells these human health vaccines primarily to physicians, wholesalers, physician distributors and government entities. A large component of pediatric and adolescent vaccine sales are made to the U.S. Centers for Disease Control and Prevention Vaccines for Children program, which is funded by the U.S. government. Additionally, the Company sells vaccines to the Federal government for placement into vaccine stockpiles. The Animal Health segment discovers, develops, manufactures and markets a wide range of veterinary pharmaceutical and vaccine products, as well as health management solutions and services, for the prevention, treatment and control of disease in all major livestock and companion animal species. The Company also offers an extensive suite of digitally connected identification, traceability and monitoring products. The Company sells its products to veterinarians, distributors and animal producers. The Healthcare Services segment provided services and solutions that focus on engagement, health analytics and clinical services to improve the value of care delivered to patients. The Company has been in the process of divesting the businesses in the Healthcare Services segment. The remaining businesses were divested during the first quarter of 2020. Sales of the Company’s products were as follows: Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019  ($ in millions) U.S. Int’l Total U.S. Int’l Total U.S. Int’l Total U.S. Int’l Total Pharmaceutical: Oncology Keytruda $ 2,157  $ 1,559  $ 3,715  $ 1,743  $ 1,327  $ 3,070  $ 6,106  $ 4,281  $ 10,387  $ 4,525  $ 3,448  $ 7,973  Alliance revenue - Lynparza (1) 107  89  196  71  53  123  297  223  519  186  126  313  Alliance revenue - Lenvima (1) 82  60  142  65  44  109  270  152  421  169  112  280  Emend 8  31  39  42  56  98  18  96  115  173  163  336  Vaccines Gardasil/Gardasil 9 579  608  1,187  761  558  1,320  1,209  1,732  2,941  1,579  1,464  3,044  ProQuad/M-M-R II/Varivax 437  139  576  482  141  623  1,033  356  1,390  1,325  469  1,794  Pneumovax 23 276  99  375  179  58  237  478  270  748  428  164  592  RotaTeq 114  96  210  102  78  180  355  246  601  360  203  564  Vaqta 32  19  51  36  26  62  79  60  139  103  65  167  Hospital Acute Care Bridion 162  157  320  133  151  284  412  431  843  381  437  817  Noxafil 13  66  79  77  100  177  27  220  247  268  291  560  Prevymis 32  46  77  22  23  45  87  113  200  60  55  115  Primaxin 1  73  74  2  75  77  2  187  189  2  204  207  Invanz 1  50  51  (1) 58  57  7  152  159  30  176  206  Cancidas 1  49  50  —  62  62  2  147  148  5  187  191  Cubicin 11  28  39  14  38  52  36  80  116  78  129  207  Zerbaxa 20  23  43  20  15  35  57  54  112  45  43  88  Immunology Simponi —  209  209  —  203  203  —  615  615  —  625  625  Remicade —  82  82  —  101  101  —  242  242  —  322  322  Neuroscience Belsomra 18  63  81  23  57  80  67  177  244  68  155  223  Virology Isentress/Isentress HD 92  113  205  102  149  250  243  403  646  304  449  752  Zepatier 6  22  28  24  59  83  38  83  122  96  208  304  Cardiovascular Zetia (1) 103  103  5  142  147  (4) 389  384  11  432  443  Vytorin 3  44  47  5  52  57  9  130  139  11  219  231  Atozet —  111  111  —  97  97  —  348  348  —  283  283  Alliance revenue - Adempas (2) 78  5  83  48  2  50  200  16  216  137  7  144  Adempas —  55  55  —  57  57  —  167  167  —  158  158  Diabetes Januvia 342  479  821  367  440  807  1,110  1,339  2,449  1,223  1,317  2,539  Janumet 105  400  506  129  375  503  361  1,138  1,499  462  1,105  1,567  Women’s Health Implanon/Nexplanon 137  52  189  136  62  199  374  142  515  421  160  581  NuvaRing 24  34  58  202  39  241  85  98  184  593  107  700  Diversified Brands Singulair 4  78  82  11  140  152  14  324  338  24  479  503  Cozaar/Hyzaar 5  86  91  6  110  116  17  275  292  16  313  329  Arcoxia —  68  68  —  72  72  —  204  204  —  221  221  Nasonex —  41  41  4  55  58  9  152  161  2  224  226  Follistim AQ 20  31  50  27  35  62  60  76  136  80  102  182  Other pharmaceutical (3) 352  834  1,186  343  804  1,149  1,144  2,334  3,478  1,037  2,394  3,431  Total Pharmaceutical segment sales 5,218  6,102  11,320  5,180  5,914  11,095  14,202  17,452  31,654  14,202  17,016  31,218  Animal Health: Livestock 164  594  758  144  582  726  448  1,697  2,145  406  1,601  2,007  Companion Animals 234  228  462  193  203  396  676  714  1,390  560  704  1,264  Total Animal Health segment sales 398  822  1,220  337  785  1,122  1,124  2,411  3,535  966  2,305  3,271  Other segment sales (4) —  —  —  46  —  46  23  —  23  133  1  133  Total segment sales 5,616  6,924  12,540  5,563  6,699  12,263  15,349  19,863  35,212  15,301  19,322  34,622  Other (5) 9  2  11  10  125  134  47  221  267  19  330  350    $ 5,625  $ 6,926  $ 12,551  $ 5,573  $ 6,824  $ 12,397  $ 15,396  $ 20,084  $ 35,479  $ 15,320  $ 19,652  $ 34,972  U.S. plus international may not equal total due to rounding. (1)    Alliance revenue represents Merck’s share of profits, which are product sales net of cost of sales and commercialization costs (see Note 3). (2)    Alliance revenue represents Merck’s share of profits from sales in Bayer’s marketing territories, which are product sales net of cost of sales and commercialization costs (see Note 3). (3)    Other pharmaceutical primarily reflects sales of other human health pharmaceutical products, including products within the franchises not listed separately. (4)    Represents sales for the Healthcare Services segment. All the businesses in the Healthcare Services segment were divested as of March 31, 2020. (5)    Other is primarily comprised of miscellaneous corporate revenues, including revenue hedging activities, as well as third-party manufacturing sales. Product sales are recorded net of the provision for discounts, including chargebacks, which are customer discounts that occur when a contracted customer purchases through an intermediary wholesale purchaser, and rebates that are owed based upon definitive contractual agreements or legal requirements with private sector and public sector (Medicaid and Medicare Part D) benefit providers, after the final dispensing of the product by a pharmacy to a benefit plan participant. These discounts, in the aggregate, reduced U.S. sales by $3.4 billion and $3.0 billion for the three months ended September 30, 2020 and 2019, respectively, and $9.6 billion and $8.6 billion for the nine months ended September 30, 2020 and 2019, respectively. Consolidated sales by geographic area where derived are as follows: Three Months Ended September 30, Nine Months Ended September 30, ($ in millions) 2020 2019 2020 2019 United States $ 5,625  $ 5,573  $ 15,396  $ 15,320  Europe, Middle East and Africa 3,454  3,189  10,059  9,452  China 1,016  914  2,715  2,423  Japan 828  919  2,506  2,639  Asia Pacific (other than China and Japan) 735  756  2,129  2,217  Latin America 604  671  1,670  1,889  Other 289  375  1,004  1,032    $ 12,551  $ 12,397  $ 35,479  $ 34,972  A reconciliation of segment profits to Income before taxes is as follows:   Three Months Ended September 30, Nine Months Ended September 30, ($ in millions) 2020 2019 2020 2019 Segment profits: Pharmaceutical segment $ 7,974  $ 7,747  $ 22,010  $ 21,437  Animal Health segment 451  423  1,336  1,243  Other segment (1) (2) 1  (2) Total segment profits 8,424  8,168  23,347  22,678  Other profits (12) 101  188  226  Unallocated: Interest income 9  61  48  225  Interest expense (203) (231) (624) (674) Depreciation and amortization (395) (382) (1,173) (1,169) Research and development (3,272) (3,110) (7,364) (7,045) Amortization of purchase accounting adjustments (285) (329) (879) (1,105) Restructuring costs (114) (232) (269) (444) Other unallocated, net (724) (1,699) (2,490) (4,019)   $ 3,428  $ 2,347  $ 10,784  $ 8,673  Pharmaceutical segment profits are comprised of segment sales less standard costs, as well as selling, general and administrative expenses directly incurred by the segment. Animal Health segment profits are comprised of segment sales, less all cost of sales, as well as selling, general and administrative expenses and research and development costs directly incurred by the segment. For internal management reporting presented to the chief operating decision maker, Merck does not allocate the remaining cost of sales not included in segment profits as described above, research and development expenses incurred in Merck Research Laboratories, the Company’s research and development division that focuses on human health-related activities, or general and administrative expenses, nor the cost of financing these activities. Separate divisions maintain responsibility for monitoring and managing these costs, including depreciation related to fixed assets utilized by these divisions and, therefore, they are not included in segment profits. In addition, costs related to restructuring activities, as well as the amortization of purchase accounting adjustments are not allocated to segments. Other profits are primarily comprised of miscellaneous corporate profits, as well as operating profits related to third-party manufacturing sales. Other unallocated, net, includes expenses from corporate and manufacturing cost centers, goodwill and other intangible asset impairment charges, gains or losses on sales of businesses, expense or income related to changes in the estimated fair value measurement of liabilities for contingent consideration, and other miscellaneous income or expense items.

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- References No definition available. + Details Name: us-gaap_SegmentReportingAbstract Namespace Prefix: us-gaap_ Data Type: xbrli:stringItemType Balance Type: na Period Type: duration

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- Definition The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 31 -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8924-108599 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 34 -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8981-108599 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 21 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8721-108599 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 40 -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9031-108599 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 32 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 32 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 26 -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8844-108599 Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 41 -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9038-108599 Reference 9: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 32 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599 Reference 10: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 22 -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8736-108599 Reference 11: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 42 -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9054-108599 Reference 12: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8657-108599 Reference 13: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 21 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8721-108599 Reference 14: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -URI http://asc.fasb.org/topic&trid=2134510 + Details Name: us-gaap_SegmentReportingDisclosureTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

v3.20.2

Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of PresentationThe accompanying unaudited condensed consolidated financial statements of Merck & Co., Inc. (Merck or the Company) have been prepared pursuant to the rules and regulations for reporting on Form 10-Q. Accordingly, certain information and disclosures required by accounting principles generally accepted in the United States (GAAP) for complete consolidated financial statements are not included herein. These interim statements should be read in conjunction with the audited financial statements and notes thereto included in Merck’s Form 10-K filed on February 26, 2020.The results of operations of any interim period are not necessarily indicative of the results of operations for the full year. In the Company’s opinion, all adjustments necessary for a fair statement of these interim statements have been included and are of a normal and recurring nature.
Recently Adopted and Issued Accounting Standards	Recently Adopted Accounting Standards In June 2016, the Financial Accounting Standards Board (FASB) issued new guidance on the accounting for credit losses on financial instruments. The new guidance introduces an expected loss model for estimating credit losses, replacing the incurred loss model. The new guidance also changes the impairment model for available-for-sale debt securities, requiring the use of an allowance to record estimated credit losses (and subsequent recoveries). The Company adopted the new guidance effective January 1, 2020. There was no impact to the Company’s consolidated financial statements upon adoption. In November 2018, the FASB issued new guidance for collaborative arrangements intended to reduce diversity in practice by clarifying whether certain transactions between collaborative arrangement participants should be accounted for under revenue recognition guidance (ASC 606). The Company adopted the new guidance effective January 1, 2020, which resulted in minor changes to the presentation of information related to the Company’s collaborative arrangements. Recently Issued Accounting Standards Not Yet Adopted In December 2019, the FASB issued amended guidance on the accounting and reporting of income taxes. The guidance is intended to simplify the accounting for income taxes by: removing exceptions related to certain intraperiod tax allocations and deferred tax liabilities; clarifying guidance primarily related to evaluating the step-up tax basis for goodwill in a business combination; and reflecting enacted changes in tax laws or rates in the annual effective tax rate. The amended guidance is effective for interim and annual periods in 2021. Early adoption is permitted. The amendments in the new guidance are to be applied on a retrospective basis, on a modified retrospective basis through a cumulative-effect adjustment to retained earnings or prospectively, depending on the amendment. The Company is currently evaluating the impact of adoption on its consolidated financial statements. In January 2020, the FASB issued new guidance intended to clarify certain interactions between accounting standards related to equity securities, equity method investments and certain derivatives. The guidance addresses accounting for the transition into and out of the equity method of accounting and measuring certain purchased options and forward contracts to acquire investments. The new guidance is effective for interim and annual periods in 2021 and is to be applied prospectively. Early adoption is permitted. The Company is currently evaluating the impact of adoption on its consolidated financial statements. In March 2020, the FASB issued optional guidance to ease the potential burden in accounting for (or recognizing the effects of) reference rate reform on financial reporting. The guidance provides optional expedients and exceptions for applying GAAP to contracts, hedging relationships, and other transactions affected by reference rate reform. The optional guidance is effective upon issuance and can be applied on a prospective basis at any time between January 1, 2020 through December 31, 2022. The Company is currently evaluating the impact of adoption on its consolidated financial statements.
Legal Costs, Policy	Legal defense costs expected to be incurred in connection with a loss contingency are accrued when probable and reasonably estimable.

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- Definition Disclosure of accounting policy for basis of accounting, or basis of presentation, used to prepare the financial statements (for example, US Generally Accepted Accounting Principles, Other Comprehensive Basis of Accounting, IFRS). + References No definition available. + Details Name: us-gaap_BasisOfAccountingPolicyPolicyTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

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- Definition Disclosure of accounting policy for legal costs incurred to protect or defend the entity's assets and rights, or to obtain assets, including monetary damages, or to obtain rights. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section S99 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=27011672&loc=d3e149975-122751 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=84158767&loc=d3e18780-107790 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=84158767&loc=d3e18726-107790 + Details Name: us-gaap_LegalCostsPolicyTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

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- Definition Disclosure of accounting policy pertaining to new accounting pronouncements that may impact the entity's financial reporting. Includes, but is not limited to, quantification of the expected or actual impact. + References No definition available. + Details Name: us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

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- References No definition available. + Details Name: us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract Namespace Prefix: us-gaap_ Data Type: xbrli:stringItemType Balance Type: na Period Type: duration

v3.20.2

Acquisitions, Research Collaborations and License Agreements (Tables)	9 Months Ended
	Sep. 30, 2020
Business Combinations [Abstract]
Fair Value of Assets Acquired and Liabilities Assumed	The estimated fair value of assets acquired and liabilities assumed from ArQule is as follows: ($ in millions) January 16, 2020 Cash and cash equivalents $ 145  IPR&D MK-1026 (formerly ARQ 531) (1) 2,280  Licensing arrangement for ARQ 087 80  Deferred income tax liabilities (389) Other assets and liabilities, net 34  Total identifiable net assets 2,150  Goodwill (2) 540  Consideration transferred $ 2,690  (1)    The estimated fair value of the identifiable intangible asset related to IPR&D was determined using an income approach. The future net cash flows were discounted to present value utilizing a discount rate of 12.5%. Actual cash flows are likely to be different than those assumed. (2)    The goodwill was allocated to the Pharmaceutical segment and is not deductible for tax purposes. The estimated fair value of assets acquired and liabilities assumed from Antelliq is as follows: ($ in millions) April 1, 2019 Cash and cash equivalents $ 31  Accounts receivable 73  Inventories 93  Property, plant and equipment 60  Identifiable intangible assets (useful lives ranging from 18-24 years) (1) 2,689  Deferred income tax liabilities (589) Other assets and liabilities, net (82) Total identifiable net assets 2,275  Goodwill (2) 1,376  Consideration transferred $ 3,651  (1)    The estimated fair values of identifiable intangible assets relate primarily to trade names and were determined using an income approach. The future net cash flows were discounted to present value utilizing a discount rate of 11.5%. Actual cash flows are likely to be different than those assumed. (2)    The goodwill recognized is largely attributable to anticipated synergies expected to arise after the acquisition and was allocated to the Animal Health segment. The goodwill is not deductible for tax purposes.

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- References No definition available. + Details Name: us-gaap_BusinessCombinationsAbstract Namespace Prefix: us-gaap_ Data Type: xbrli:stringItemType Balance Type: na Period Type: duration

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- Definition Tabular disclosure of the amounts recognized as of the acquisition date for each major class of assets acquired and liabilities assumed. May include but not limited to the following: (a) acquired receivables; (b) contingencies recognized at the acquisition date; and (c) the fair value of noncontrolling interests in the acquiree. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=121647850&loc=d3e4845-128472 + Details Name: us-gaap_ScheduleOfRecognizedIdentifiedAssetsAcquiredAndLiabilitiesAssumedTableTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

v3.20.2

Collaborative Arrangements (Tables)	9 Months Ended
	Sep. 30, 2020
Collaborative Arrangements [Abstract]
Collaboration Arrangements	Summarized financial information related to this collaboration is as follows: Three Months Ended September 30, Nine Months Ended September 30, ($ in millions) 2020 2019 2020 2019 Alliance revenue - Lynparza $ 196  $ 123  $ 519  $ 313  Alliance revenue - Koselugo 3  —  3  —  Total alliance revenue $ 199  $ 123  $ 522  $ 313  Cost of sales (1) 41  28  205  120  Selling, general and administrative 40  36  112  96  Research and development 20  44  93  122  ($ in millions) September 30, 2020 December 31, 2019 Receivables from AstraZeneca included in Other current assets $ 197  $ 128  Payables to AstraZeneca included in Accrued and other current liabilities (2) 309  577  Payables to AstraZeneca included in Other Noncurrent Liabilities (2) 400  —  (1) Represents amortization of capitalized milestone payments. (2) Includes accrued milestone payments. Summarized financial information related to this collaboration is as follows: Three Months Ended September 30, Nine Months Ended September 30, ($ in millions) 2020 2019 2020 2019 Alliance revenue - Lenvima $ 142  $ 109  $ 421  $ 280  Cost of sales (1) 46  23  215  97  Selling, general and administrative 18  21  48  59  Research and development 48  37  168  146  ($ in millions) September 30, 2020 December 31, 2019 Receivables from Eisai included in Other current assets $ 170  $ 150  Payables to Eisai included in Accrued and other current liabilities (2) 325  700  Payables to Eisai included in Other Noncurrent Liabilities (3) 570  525  (1) Represents amortization of capitalized milestone payments. (2) Includes accrued milestone and future option payments. (3) Includes accrued milestone payments. Summarized financial information related to this collaboration is as follows: Three Months Ended September 30, Nine Months Ended September 30, ($ in millions) 2020 2019 2020 2019 Alliance revenue - Adempas $ 83  $ 50  $ 216  $ 144  Net sales of Adempas recorded by Merck 55  57  167  158  Total sales $ 138  $ 107  $ 383  $ 302  Cost of sales (1) 29  28  85  86  Selling, general and administrative 19  12  42  31  Research and development 12  31  53  94  ($ in millions) September 30, 2020 December 31, 2019 Receivables from Bayer included in Other current assets $ 70  $ 49  Payables to Bayer included in Other Noncurrent Liabilities (2) 375  375  (1) Includes amortization of intangible assets. (2) Represents accrued milestone payment.

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- Definition Collaborative Arrangements [Abstract] + References No definition available. + Details Name: mrk_CollaborativeArrangementsAbstract Namespace Prefix: mrk_ Data Type: xbrli:stringItemType Balance Type: na Period Type: duration

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- Definition Tabular disclosure of collaborative arrangement and arrangement other than collaborative applicable to revenue-generating activity or operations. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 808 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6931272&loc=SL5834143-161434 + Details Name: us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTableTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

v3.20.2

Restructuring (Tables)	9 Months Ended
	Sep. 30, 2020
Restructuring and Related Activities [Abstract]
Charges Related to Restructuring Program Activities by Type of Cost	The following tables summarize the charges related to restructuring program activities by type of cost:   Three Months Ended September 30, 2020 Nine Months Ended September 30, 2020 ($ in millions) Separation Costs Accelerated Depreciation Other Total Separation Costs Accelerated Depreciation Other Total Cost of sales $ —  $ 33  $ 5  $ 38  $ —  $ 89  $ 42  $ 131  Selling, general and administrative —  15  —  15  —  37  —  37  Research and development —  18  1  19  —  66  1  67  Restructuring costs 61  —  53  114  143  —  126  269  $ 61  $ 66  $ 59  $ 186  $ 143  $ 192  $ 169  $ 504    Three Months Ended September 30, 2019 Nine Months Ended September 30, 2019 ($ in millions) Separation Costs Accelerated Depreciation Other Total Separation Costs Accelerated Depreciation Other Total Cost of sales $ —  $ 41  $ 21  $ 62  $ —  $ 139  $ 22  $ 161  Selling, general and administrative —  1  —  1  —  33  —  33  Research and development —  (1) 2  1  —  1  3  4  Restructuring costs 205  —  27  232  358  —  86  444  $ 205  $ 41  $ 50  $ 296  $ 358  $ 173  $ 111  $ 642
Charges and Spending Relating to Restructuring Activities by Program	The following table summarizes the charges and spending relating to restructuring program activities for the nine months ended September 30, 2020: ($ in millions) Separation Costs Accelerated Depreciation Other Total Restructuring reserves January 1, 2020 $ 690  $ —  $ 69  $ 759  Expense 143  192  169  504  (Payments) receipts, net (395) —  (237) (632) Non-cash activity —  (192) 39  (153) Restructuring reserves September 30, 2020 (1) $ 438  $ —  $ 40  $ 478  (1)The remaining cash outlays are expected to be substantially completed by the end of 2023.

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- References No definition available. + Details Name: us-gaap_RestructuringAndRelatedActivitiesAbstract Namespace Prefix: us-gaap_ Data Type: xbrli:stringItemType Balance Type: na Period Type: duration

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- Definition Tabular disclosure of costs incurred for restructuring including, but not limited to, exit and disposal activities, remediation, implementation, integration, asset impairment, and charges against earnings from the write-down of assets. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 5.P.3) -URI http://asc.fasb.org/extlink&oid=115931487&loc=d3e140864-122747 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SAB TOPIC 5.P.4) -URI http://asc.fasb.org/extlink&oid=115931487&loc=d3e140904-122747 + Details Name: us-gaap_ScheduleOfRestructuringAndRelatedCostsTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

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- Definition Tabular disclosure of an entity's restructuring reserve that occurred during the period associated with the exit from or disposal of business activities or restructurings for each major type of cost. This element may also include a description of any reversal and other adjustment made during the period to the amount of an accrued liability for restructuring activities. This element may be used to encapsulate the roll forward presentations of an entity's restructuring reserve by type of cost and in total, and explanation of changes that occurred in the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b)(2) -URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SAB Topic 5.P.4(b)(2)) -URI http://asc.fasb.org/extlink&oid=115931487&loc=d3e140904-122747 + Details Name: us-gaap_ScheduleOfRestructuringReserveByTypeOfCostTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

v3.20.2

Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Effect of Net Investment Hedges on OCI and the Consolidated Statement of Income	The effects of the Company’s net investment hedges on OCI and the Consolidated Statement of Income are shown below: Amount of Pretax (Gain) Loss Recognized in Other Comprehensive Income (1) Amount of Pretax (Gain) Loss Recognized in Other (income) expense, net for Amounts Excluded from Effectiveness Testing Three Months Ended September 30, Nine Months Ended September 30, Three Months Ended September 30, Nine Months Ended September 30, ($ in millions) 2020 2019 2020 2019 2020 2019 2020 2019 Net Investment Hedging Relationships Foreign exchange contracts $ 10  $ 1  $ 15  $ 8  $ (4) $ (8) $ (15) $ (23) Euro-denominated notes 162  (150) 182  (152) —  —  —  —  (1) No amounts were reclassified from AOCI into income related to the sale of a subsidiary.
Summary of Interest Rate Swaps Held	At September 30, 2020, the Company was a party to 14 pay-floating, receive-fixed interest rate swap contracts designated as fair value hedges of fixed-rate notes in which the notional amounts match the amount of the hedged fixed-rate notes as detailed in the table below. September 30, 2020 ($ in millions) Par Value of Debt Number of Interest Rate Swaps Held Total Swap Notional Amount 3.875% notes due 2021 $ 1,150  5  $ 1,150  2.40% notes due 2022 1,000  4  1,000  2.35% notes due 2022 1,250  5  1,250
Amounts Recorded on Balance Sheet Related to Fair Value Hedges	The table below presents the location of amounts recorded on the Consolidated Balance Sheet related to cumulative basis adjustments for fair value hedges: Carrying Amount of Hedged Liabilities Cumulative Amount of Fair Value Hedging Adjustment Increase (Decrease) Included in the Carrying Amount ($ in millions) September 30, 2020 December 31, 2019 September 30, 2020 December 31, 2019 Balance Sheet Line Item in which Hedged Item is Included Loans payable and current portion of long-term debt $ 1,155  $ 1,249  $ 5  $ (1) Long-Term Debt 2,309  3,409  62  14
Fair Value of Derivatives on a Gross Basis Segregated between those Derivatives that are Designated as Hedging Instruments and those that are Not Designated as Hedging Instruments	Presented in the table below is the fair value of derivatives on a gross basis segregated between those derivatives that are designated as hedging instruments and those that are not designated as hedging instruments:     September 30, 2020 December 31, 2019     Fair Value of Derivative U.S. Dollar Notional Fair Value of Derivative U.S. Dollar Notional ($ in millions) Balance Sheet Caption Asset Liability Asset Liability Derivatives Designated as Hedging Instruments Interest rate swap contracts Other current assets $ 6  $ —  $ 1,150  $ —  $ —  $ —  Interest rate swap contracts Other Assets 63  —  2,250  15  —  3,400  Interest rate swap contracts Accrued and other current liabilities —  —  —  —  1  1,250  Foreign exchange contracts Other current assets 30  —  4,120  152  —  6,117  Foreign exchange contracts Other Assets 59  —  1,881  55  —  2,160  Foreign exchange contracts Accrued and other current liabilities —  104  3,096  —  22  1,748  Foreign exchange contracts Other Noncurrent Liabilities —  1  157  —  1  53      $ 158  $ 105  $ 12,654  $ 222  $ 24  $ 14,728  Derivatives Not Designated as Hedging Instruments               Foreign exchange contracts Other current assets $ 81  $ —  $ 5,455  $ 66  $ —  $ 7,245  Foreign exchange contracts Accrued and other current liabilities —  171  8,042  —  73  8,693  Forward contract related to Seagen common stock Accrued and other current liabilities —  22  1,000  —  —  —      $ 81  $ 193  $ 14,497  $ 66  $ 73  $ 15,938      $ 239  $ 298  $ 27,151  $ 288  $ 97  $ 30,666
Information on Derivative Positions Subject to Master Netting Arrangements as if they were Presented on a Net Basis	The following table provides information on the Company’s derivative positions subject to these master netting arrangements as if they were presented on a net basis, allowing for the right of offset by counterparty and cash collateral exchanged per the master agreements and related credit support annexes:   September 30, 2020 December 31, 2019 ($ in millions) Asset Liability Asset Liability Gross amounts recognized in the condensed consolidated balance sheet $ 239  $ 298  $ 288  $ 97  Gross amounts subject to offset in master netting arrangements not offset in the condensed consolidated balance sheet (140) (140) (84) (84) Cash collateral received —  —  (34) —  Net amounts $ 99  $ 158  $ 170  $ 13
Location and Amount of Pretax (Gains) Losses of Derivatives	The table below provides information regarding the location and amount of pretax (gains) losses of derivatives designated in fair value or cash flow hedging relationships: Sales Other (income) expense, net (1) Other comprehensive income (loss) Sales Other (income) expense, net (1) Other comprehensive income (loss) Three Months Ended September 30, Three Months Ended September 30, Three Months Ended September 30, Nine Months Ended September 30, Nine Months Ended September 30, Nine Months Ended September 30, ($ in millions) 2020 2019 2020 2019 2020 2019 2020 2019 2020 2019 2020 2019 Financial Statement Line Items in which Effects of Fair Value or Cash Flow Hedges are Recorded $ 12,551  $ 12,397  $ (312) $ 35  $ 10  $ (28) $ 35,479  $ 34,972  $ (630) $ 362  $ (190) $ 155  (Gain) loss on fair value hedging relationships Interest rate swap contracts Hedged items —  —  (14) 13  —  —  —  —  54  101  —  —  Derivatives designated as hedging instruments —  —  —  (6) —  —  —  —  (76) (74) —  —  Impact of cash flow hedging relationships Foreign exchange contracts Amount of (loss) gain recognized in OCI on derivatives —  —  —  —  (195) 186  —  —  —  —  (126) 183  Increase (decrease) in Sales as a result of AOCI reclassifications (23) 70  —  —  23  (70) 65  189  —  —  (65) (189) Interest rate contracts Amount of gain recognized in Other (income) expense, net on derivatives —  —  (1) (1) —  —  —  —  (3) (3) —  —  Amount of loss recognized in OCI on derivatives —  —  —  —  (1) (1) —  —  —  —  (3) (6) (1) Interest expense is a component of Other (income) expense, net.
Income Statement Effects of Derivatives Not Designated as Hedging Instruments	The table below provides information regarding the income statement effects of derivatives not designated as hedging instruments: Amount of Derivative Pretax (Gain) Loss Recognized in Income Three Months Ended September 30, Nine Months Ended September 30, ($ in millions) Income Statement Caption 2020 2019 2020 2019 Derivatives Not Designated as Hedging Instruments Foreign exchange contracts (1) Other (income) expense, net $ (7) $ (8) $ (138) $ 112  Foreign exchange contracts (2) Sales 7  (11) 4  (7) Interest rate contracts (3) Other (income) expense, net —  —  9  —  Forward contract related to Seagen common stock Research and development expenses 22  —  22  —  (1) These derivative contracts mitigate changes in the value of remeasured foreign currency denominated monetary assets and liabilities attributable to changes in foreign currency exchange rates. (2) These derivative contracts serve as economic hedges of forecasted transactions. (3) These derivatives serve as economic hedges against rising treasury rates.
Information on Investments in Debt and Equity Securities	Information on investments in debt and equity securities is as follows:   September 30, 2020 December 31, 2019   Amortized Cost Gross Unrealized Fair Value Amortized Cost Gross Unrealized Fair Value ($ in millions) Gains Losses Gains Losses U.S. government and agency securities $ 74  $ —  $ —  $ 74  $ 266  $ 3  $ —  $ 269  Foreign government bonds 2  —  —  2  —  —  —  —  Commercial paper —  —  —  —  668  —  —  668  Corporate notes and bonds —  —  —  —  608  13  —  621  Asset-backed securities —  —  —  —  226  1  —  227  Total debt securities $ 76  $ —  $ —  $ 76  $ 1,768  $ 17  $ —  $ 1,785  Publicly traded equity securities (1) 1,477  838  Total debt and publicly traded equity securities $ 1,553  $ 2,623  (1) Unrealized net (gains) losses recognized in Other (income) expense, net on equity securities still held at September 30, 2020 were $(43) million and $(512) million in the third quarter and first nine months of 2020, respectively. Unrealized net losses (gains) recognized in Other (income) expense, net on equity securities still held at September 30, 2019 were $25 million and $(41) million in the third quarter and first nine months of 2019, respectively.
Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis	Financial assets and liabilities measured at fair value on a recurring basis are summarized below: Fair Value Measurements Using Fair Value Measurements Using   Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total ($ in millions) September 30, 2020 December 31, 2019 Assets Investments Foreign government bonds $ —  $ 2  $ —  $ 2  $ —  $ —  $ —  $ —  Commercial paper —  —  —  —  —  668  —  668  Corporate notes and bonds —  —  —  —  —  621  —  621  Asset-backed securities (1) —  —  —  —  —  227  —  227  U.S. government and agency securities —  —  —  —  —  209  —  209  Publicly traded equity securities 1,370  —  —  1,370  518  —  —  518    1,370  2  —  1,372  518  1,725  —  2,243  Other assets (2) U.S. government and agency securities 74  —  —  74  60  —  —  60  Publicly traded equity securities 107  —  —  107  320  —  —  320  181  —  —  181  380  —  —  380  Derivative assets (3) Forward exchange contracts —  116  —  116  —  169  —  169  Interest rate swaps —  69  —  69  —  15  —  15  Purchased currency options —  54  —  54  —  104  —  104    —  239  —  239  —  288  —  288  Total assets $ 1,551  $ 241  $ —  $ 1,792  $ 898  $ 2,013  $ —  $ 2,911  Liabilities Other liabilities Contingent consideration $ —  $ —  $ 829  $ 829  $ —  $ —  $ 767  $ 767  Derivative liabilities (3) Forward exchange contracts —  275  —  275  —  95  —  95  Forward contract related to Seagen common stock —  22  —  22  —  —  —  —  Written currency options —  1  —  1  —  1  —  1  Interest rate swaps —  —  —  —  —  1  —  1  —  298  —  298  —  97  —  97  Total liabilities $ —  $ 298  $ 829  $ 1,127  $ —  $ 97  $ 767  $ 864  (1)Primarily all of the asset-backed securities were highly rated (Standard & Poor’s rating of AAA and Moody’s Investors Service rating of Aaa), secured primarily by auto loan, credit card and student loan receivables, with weighted-average lives of primarily 5 years or less. (2)    Investments included in other assets are restricted as to use, including for the payment of benefits under employee benefit plans. (3)    The fair value determination of derivatives includes the impact of the credit risk of counterparties to the derivatives and the Company’s own credit risk, the effects of which were not significant.
Information About the Changes in Liabilities for Contingent Consideration	Summarized information about the changes in liabilities for contingent consideration associated with business acquisitions is as follows: Nine Months Ended September 30, ($ in millions) 2020 2019 Fair value January 1 $ 767  $ 788  Additions 97  —  Changes in estimated fair value (1) 71  52  Payments (106) (85) Fair value September 30 (2)(3) $ 829  $ 755  (1) Recorded in Cost of sales, Research and development expenses, and Other (income) expense, net. Includes cumulative translation adjustments. (2) Balance at September 30, 2020 includes $140 million recorded as a current liability for amounts expected to be paid within the next 12 months. (3) At September 30, 2020 and December 31, 2019, $637 million and $625 million, respectively, of the liabilities relate to the termination of the Sanofi-Pasteur MSD joint venture in 2016. As part of the termination, Merck recorded a liability for contingent future royalty payments of 11.5% on net sales of all Merck products that were previously sold by the joint venture through December 31, 2024. The fair value of this liability is determined utilizing the estimated amount and timing of projected cash flows using a risk-adjusted discount rate of 8% to present value the cash flows.

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- Definition Tabular disclosure of the fair value measurement of liabilities using significant unobservable inputs (Level 3), a reconciliation of the beginning and ending balances, separately presenting changes attributable to the following: (1) total gains or losses for the period (realized and unrealized), segregating those gains or losses included in earnings (or changes in net assets), and gains or losses recognized in other comprehensive income (loss) and a description of where those gains or losses included in earnings (or changes in net assets) are reported in the statement of income (or activities); (2) purchases, sales, issues, and settlements (each type disclosed separately); and (3) transfers in and transfers out of Level 3 (for example, transfers due to changes in the observability of significant inputs) by class of liability. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19279-110258 + Details Name: us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

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- Definition Tabular disclosure of the reconciliation of available-for-sale securities from cost basis to fair value. + References No definition available. + Details Name: us-gaap_ScheduleOfAvailableForSaleSecuritiesReconciliationTableTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

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- Definition Tabular disclosure of the location and amount of derivative instruments and nonderivative instruments designated as hedging instruments reported before netting adjustments, and the amount of gain (loss) on derivative instruments and nonderivative instruments designated and qualified as hedging instruments. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4E -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5624181-113959 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5618551-113959 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5624171-113959 + Details Name: us-gaap_ScheduleOfDerivativeInstrumentsGainLossInStatementOfFinancialPerformanceTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

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- Definition Tabular disclosure of the location and fair value amounts of derivative instruments (and nonderivative instruments that are designated and qualify as hedging instruments) reported in the statement of financial position. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4B -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5624163-113959 + Details Name: us-gaap_ScheduleOfDerivativeInstrumentsInStatementOfFinancialPositionFairValueTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

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- Definition Tabular disclosure of assets and liabilities, including [financial] instruments measured at fair value that are classified in stockholders' equity, if any, that are measured at fair value on a recurring basis. The disclosures contemplated herein include the fair value measurements at the reporting date by the level within the fair value hierarchy in which the fair value measurements in their entirety fall, segregating fair value measurements using quoted prices in active markets for identical assets (Level 1), significant other observable inputs (Level 2), and significant unobservable inputs (Level 3). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details Name: us-gaap_ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

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- Definition Tabular disclosure for fair value hedging instruments of (a) the location and amount of gains and losses reported in the statement of financial performance and (b) the location and fair value amounts of the instruments reported in the statement of financial position. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5624171-113959 + Details Name: us-gaap_ScheduleOfFairValueHedgingInstrumentsStatementsOfFinancialPerformanceAndFinancialPositionLocationTableTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

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- Definition Tabular disclosure of interest rate derivatives, including, but not limited to, the fair value of the derivatives, statement of financial position location, and statement of financial performance location of these instruments. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5624171-113959 + Details Name: us-gaap_ScheduleOfInterestRateDerivativesTableTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

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- Definition Tabular disclosure of the effective portion of gains and losses on derivative instruments (and nonderivative instruments) designated and qualifying in net investment hedges recorded in accumulated other comprehensive income (loss) during the term of the hedging relationship and reclassified into earnings during the current period. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4CCC -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL109998896-113959 + Details Name: us-gaap_ScheduleOfNetInvestmentHedgesInAccumulatedOtherComprehensiveIncomeLossTableTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

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- Definition Tabular disclosure of derivative instrument not designated or qualifying as hedging instrument. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5624171-113959 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4CC -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL109998890-113959 + Details Name: us-gaap_ScheduleOfOtherDerivativesNotDesignatedAsHedgingInstrumentsStatementsOfFinancialPerformanceAndFinancialPositionLocationTableTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

v3.20.2

Inventories (Tables)	9 Months Ended
	Sep. 30, 2020
Inventory Disclosure [Abstract]
Schedule of Inventories	Inventories consisted of: ($ in millions) September 30, 2020 December 31, 2019 Finished goods $ 2,038  $ 1,772  Raw materials and work in process 6,073  5,650  Supplies 197  207  Total (approximates current cost) 8,308  7,629  Decrease to LIFO cost (99) (171)   $ 8,209  $ 7,458  Recognized as: Inventories $ 6,128  $ 5,978  Other assets 2,081  1,480

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- Definition Tabular disclosure of the carrying amount as of the balance sheet date of merchandise, goods, commodities, or supplies held for future sale or to be used in manufacturing, servicing or production process. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(6)(c)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(6)(b)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(6)(a)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6361739&loc=d3e7789-107766 + Details Name: us-gaap_ScheduleOfInventoryCurrentTableTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

v3.20.2

Equity (Tables)	9 Months Ended
	Sep. 30, 2020
Equity [Abstract]
Equity	Three Months Ended September 30,      Common Stock Other Paid-In Capital Retained Earnings Accumulated Other Comprehensive Loss   Treasury Stock Non- controlling Interests Total ($ and shares in millions except per share amounts) Shares Par Value Shares Cost Balance at July 1, 2019 3,577  $ 1,788  $ 39,484  $ 45,295  $ (5,362) 1,010  $ (53,570) $ 102  $ 27,737  Net income attributable to Merck & Co., Inc. —  —  —  1,901  —  —  —  —  1,901  Other comprehensive loss, net of taxes —  —  —  —  (28) —  —  —  (28) Cash dividends declared on common stock ($0.55 per share) —  —  —  (1,392) —  —  —  —  (1,392) Treasury stock shares purchased —  —  —  —  —  17  (1,405) —  (1,405) Share-based compensation plans and other —  —  77  —  —  (1) 50  —  127  Net income attributable to noncontrolling interests —  —  —  —  —  —  —  6  6  Distributions attributable to noncontrolling interests —  —  —  —  —  —  —  (21) (21) Balance at September 30, 2019 3,577  $ 1,788  $ 39,561  $ 45,804  $ (5,390) 1,026  $ (54,925) $ 87  $ 26,925  Balance at July 1, 2020 3,577  $ 1,788  $ 39,373  $ 49,724  $ (6,393) 1,048  $ (56,850) $ 102  $ 27,744  Net income attributable to Merck & Co., Inc. —  —  —  2,941  —  —  —  —  2,941  Other comprehensive income, net of taxes —  —  —  —  10  —  —  —  10  Cash dividends declared on common stock ($0.61 per share) —  —  —  (1,558) —  —  —  —  (1,558) Share-based compensation plans and other —  —  116  —  —  (1) 35  —  151  Net income attributable to noncontrolling interests —  —  —  —  —  —  —  4  4  Distributions attributable to noncontrolling interests —  —  —  —  —  —  —  (22) (22) Balance at September 30, 2020 3,577  $ 1,788  $ 39,489  $ 51,107  $ (6,383) 1,047  $ (56,815) $ 84  $ 29,270  Nine Months Ended September 30,      Common Stock Other Paid-In Capital Retained Earnings Accumulated Other Comprehensive Loss   Treasury Stock Non- controlling Interests Total ($ and shares in millions except per share amounts) Shares Par Value Shares Cost Balance at January 1, 2019 3,577  $ 1,788  $ 38,808  $ 42,579  $ (5,545) 985  $ (50,929) $ 181  $ 26,882  Net income attributable to Merck & Co., Inc. —  —  —  7,487  —  —  —  —  7,487  Other comprehensive income, net of taxes —  —  —  —  155  —  —  —  155  Cash dividends declared on common stock ($1.65 per share) —  —  —  (4,262) —  —  —  —  (4,262) Treasury stock shares purchased —  —  1,000  —  —  54  (4,730) —  (3,730) Share-based compensation plans and other —  —  (247) —  —  (13) 734  —  487  Net loss attributable to noncontrolling interests —  —  —  —  —  —  —  (73) (73) Distributions attributable to noncontrolling  interests —  —  —  —  —  —  —  (21) (21) Balance at September 30, 2019 3,577  1,788  39,561  45,804  (5,390) 1,026  (54,925) 87  26,925  Balance at January 1, 2020 3,577  $ 1,788  $ 39,660  $ 46,602  $ (6,193) 1,038  $ (55,950) $ 94  $ 26,001  Net income attributable to Merck & Co., Inc. —  —  —  9,161  —  —  —  —  9,161  Other comprehensive loss, net of taxes —  —  —  —  (190) —  —  —  (190) Cash dividends declared on common stock ($1.83 per share) —  —  —  (4,656) —  —  —  —  (4,656) Treasury stock shares purchased —  —  —  —  —  16  (1,281) —  (1,281) Share-based compensation plans and other —  —  (171) —  —  (7) 416  —  245  Net income attributable to noncontrolling interests —  —  —  —  —  —  —  12  12  Distributions attributable to noncontrolling  interests —  —  —  —  —  —  —  (22) (22) Balance at September 30, 2020 3,577  $ 1,788  $ 39,489  $ 51,107  $ (6,383) 1,047  $ (56,815) $ 84  $ 29,270

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- Definition Tabular disclosure of changes in the separate accounts comprising stockholders' equity (in addition to retained earnings) and of the changes in the number of shares of equity securities during at least the most recent annual fiscal period and any subsequent interim period presented is required to make the financial statements sufficiently informative if both financial position and results of operations are presented. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644 + Details Name: us-gaap_ScheduleOfStockholdersEquityTableTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

v3.20.2

Share-Based Compensation Plans (Tables)	9 Months Ended
	Sep. 30, 2020
Share-based Payment Arrangement [Abstract]
Amounts of Share-Based Compensation Cost Recorded in Consolidated Statement of Income	The following table provides the amounts of share-based compensation cost recorded in the Condensed Consolidated Statement of Income:   Three Months Ended September 30, Nine Months Ended September 30, ($ in millions) 2020 2019 2020 2019 Pretax share-based compensation expense $ 126  $ 101  $ 354  $ 306  Income tax benefit (17) (14) (48) (42) Total share-based compensation expense, net of taxes $ 109  $ 87  $ 306  $ 264
Assumptions Used to Determine Weighted-Average Fair Value of Options Granted	During the first nine months of 2020, the Company granted 4 million stock options with a weighted-average exercise price of $77.67 per option and during the first nine months of 2019 granted 3 million stock options with a weighted-average exercise price of $80.05 per option. The weighted-average fair value of options granted during the first nine months of 2020 and 2019 was $9.93 and $10.63 per option, respectively, and was determined using the following assumptions:    Nine Months Ended September 30, 2020 2019 Expected dividend yield 3.1  % 3.2  % Risk-free interest rate 0.4  % 2.4  % Expected volatility 22.1  % 18.7  % Expected life (years) 5.8 5.9

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- Definition Tabular disclosure of allocation of amount expensed and capitalized for award under share-based payment arrangement to statement of income or comprehensive income and statement of financial position. Includes, but is not limited to, corresponding line item in financial statement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 14.F) -URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5047-113901 + Details Name: us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

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- Definition Tabular disclosure of the significant assumptions used during the year to estimate the fair value of stock options, including, but not limited to: (a) expected term of share options and similar instruments, (b) expected volatility of the entity's shares, (c) expected dividends, (d) risk-free rate(s), and (e) discount for post-vesting restrictions. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 + Details Name: us-gaap_ScheduleOfShareBasedPaymentAwardStockOptionsValuationAssumptionsTableTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

v3.20.2

Pension and Other Postretirement Benefit Plans (Tables)	9 Months Ended
	Sep. 30, 2020
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Components of net cost of defined benefit plans	The Company has defined benefit pension plans covering eligible employees in the United States and in certain of its international subsidiaries. The net periodic benefit cost of such plans consisted of the following components:     Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 ($ in millions) U.S. International U.S. International U.S. International U.S. International Service cost $ 96  $ 77  $ 76  $ 58  $ 270  $ 225  $ 221  $ 178  Interest cost 107  35  115  44  323  103  343  133  Expected return on plan assets (193) (104) (202) (106) (581) (310) (613) (320) Amortization of unrecognized prior service credit (12) (3) (12) (3) (37) (9) (37) (9) Net loss amortization 75  32  43  16  228  94  113  47  Termination benefits 1  1  3  —  5  2  7  1  Curtailments 1  —  5  —  4  (1) 6  —  Settlements 2  —  —  —  11  2  —  —    $ 77  $ 38  $ 28  $ 9  $ 223  $ 106  $ 40  $ 30
Other Postretirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Components of net cost of defined benefit plans	The Company provides medical benefits, principally to its eligible U.S. retirees and similar benefits to their dependents, through its other postretirement benefit plans. The net credit of such plans consisted of the following components:     Three Months Ended September 30, Nine Months Ended September 30, ($ in millions) 2020 2019 2020 2019 Service cost $ 13  $ 12  $ 39  $ 36  Interest cost 14  17  43  52  Expected return on plan assets (19) (18) (56) (54) Amortization of unrecognized prior service credit (18) (20) (54) (59) Net gain amortization (5) (3) (13) (7) Termination benefits —  1  —  1  Curtailments —  (3) (1) (4)   $ (15) $ (14) $ (42) $ (35)

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- Definition Tabular disclosure of the components of net benefit costs for pension plans and/or other employee benefit plans including service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) recognized due to settlements or curtailments. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details Name: us-gaap_ScheduleOfNetBenefitCostsTableTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

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- Details Name: us-gaap_RetirementPlanTypeAxis=us-gaap_PensionPlansDefinedBenefitMember Namespace Prefix: Data Type: na Balance Type: Period Type:

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- Details Name: us-gaap_RetirementPlanTypeAxis=us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember Namespace Prefix: Data Type: na Balance Type: Period Type:

v3.20.2

Other (Income) Expense, Net (Tables)	9 Months Ended
	Sep. 30, 2020
Other Income and Expenses [Abstract]
Other (Income) Expense, Net	Other (income) expense, net, consisted of:    Three Months Ended September 30, Nine Months Ended September 30, ($ in millions) 2020 2019 2020 2019 Interest income $ (9) $ (61) $ (48) $ (225) Interest expense 203  231  624  674  Exchange losses 10  38  89  166  Income from investments in equity securities, net (1) (360) (16) (964) (50) Net periodic defined benefit plan (credit) cost other than service cost (88) (128) (259) (409) Other, net (68) (29) (72) 206    $ (312) $ 35  $ (630) $ 362  (1)    Includes net realized and unrealized gains and losses from investments in equity securities either owned directly or through ownership interests in investment funds. Unrealized gains and losses from investments that are directly owned are determined at the end of the reporting period, while ownership interests in investment funds are accounted for on a one quarter lag.

X

- References No definition available. + Details Name: us-gaap_OtherIncomeAndExpensesAbstract Namespace Prefix: us-gaap_ Data Type: xbrli:stringItemType Balance Type: na Period Type: duration

X

- Definition Tabular disclosure of the components of non-operating income or non-operating expense that may include amounts earned from dividends, interest on securities, gains (losses) on securities sold, equity earnings of unconsolidated affiliates, net gain (loss) on sales of business, interest expense and other miscellaneous income or expense items. + References No definition available. + Details Name: us-gaap_ScheduleOfOtherNonoperatingIncomeExpenseTableTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

v3.20.2

Earnings Per Share (Tables)	9 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
Calculations of Earnings Per Share	The calculations of earnings per share are as follows:   Three Months Ended September 30, Nine Months Ended September 30, ($ and shares in millions except per share amounts) 2020 2019 2020 2019 Net income attributable to Merck & Co., Inc. $ 2,941  $ 1,901  $ 9,161  $ 7,487  Average common shares outstanding 2,529  2,558  2,530  2,572  Common shares issuable (1) 9  14  11  15  Average common shares outstanding assuming dilution 2,538  2,572  2,541  2,587  Basic earnings per common share attributable to Merck & Co., Inc. common shareholders $ 1.16  $ 0.74  $ 3.62  $ 2.91  Earnings per common share assuming dilution attributable to Merck & Co., Inc. common shareholders $ 1.16  $ 0.74  $ 3.61  $ 2.89  (1)Issuable primarily under share-based compensation plans.

X

- References No definition available. + Details Name: us-gaap_EarningsPerShareAbstract Namespace Prefix: us-gaap_ Data Type: xbrli:stringItemType Balance Type: na Period Type: duration

X

- Definition Tabular disclosure of an entity's basic and diluted earnings per share calculations, including a reconciliation of numerators and denominators of the basic and diluted per-share computations for income from continuing operations. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257 + Details Name: us-gaap_ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

v3.20.2

Other Comprehensive Income (Loss) (Tables)	9 Months Ended
	Sep. 30, 2020
Equity [Abstract]
Changes in AOCI by Component	Changes in AOCI by component are as follows: Three Months Ended September 30, ($ in millions) Derivatives Investments Employee Benefit Plans Cumulative Translation Adjustment Accumulated Other Comprehensive Income (Loss) Balance July 1, 2019, net of taxes $ 66  $ 48  $ (3,530) $ (1,946) $ (5,362) Other comprehensive income (loss) before reclassification adjustments, pretax 186  8  (4) (84) 106  Tax (39) —  —  (33) (72) Other comprehensive income (loss) before reclassification adjustments, net of taxes 147  8  (4) (117) 34  Reclassification adjustments, pretax (71) (1) (25) (2) 21  (3) —  (75) Tax 15  —  (2) —  13  Reclassification adjustments, net of taxes (56) (25) 19  —  (62) Other comprehensive income (loss), net of taxes 91  (17) 15  (117) (28) Balance September 30, 2019, net of taxes $ 157  $ 31  $ (3,515) $ (2,063) $ (5,390) Balance July 1, 2020, net of taxes $ 15  $ —  $ (4,162) $ (2,246) $ (6,393) Other comprehensive income (loss) before reclassification adjustments, pretax (195) —  2  50  (143) Tax 41  —  1  35  77  Other comprehensive income (loss) before reclassification adjustments, net of taxes (154) —  3  85  (66) Reclassification adjustments, pretax 22  (1) —  72  (3) —  94  Tax (5) —  (13) —  (18) Reclassification adjustments, net of taxes 17  —  59  —  76  Other comprehensive income (loss), net of taxes (137) —  62  85  10  Balance September 30, 2020, net of taxes $ (122) $ —  $ (4,100) $ (2,161) $ (6,383) Nine Months Ended September 30, ($ in millions) Derivatives Investments Employee Benefit Plans Cumulative Translation Adjustment Accumulated Other Comprehensive Income (Loss) Balance January 1, 2019, net of taxes $ 166  $ (78) $ (3,556) $ (2,077) $ (5,545) Other comprehensive income (loss) before reclassification adjustments, pretax 183  139  (5) 47  364  Tax (38) —  6  (33) (65) Other comprehensive income (loss) before reclassification adjustments, net of taxes 145  139  1  14  299  Reclassification adjustments, pretax (195) (1) (30) (2) 49  (3) —  (176) Tax 41  —  (9) —  32  Reclassification adjustments, net of taxes (154) (30) 40  —  (144) Other comprehensive income (loss), net of taxes (9) 109  41  14  155  Balance September 30, 2019, net of taxes $ 157  $ 31  $ (3,515) $ (2,063) $ (5,390) Balance January 1, 2020, net of taxes $ 31  $ 18  $ (4,261) $ (1,981) $ (6,193) Other comprehensive income (loss) before reclassification adjustments, pretax (126) 3  (19) (220) (362) Tax 27  —  12  40  79  Other comprehensive income (loss) before reclassification adjustments, net of taxes (99) 3  (7) (180) (283) Reclassification adjustments, pretax (68) (1) (21) (2) 210  (3) —  121  Tax 14  —  (42) —  (28) Reclassification adjustments, net of taxes (54) (21) 168  —  93  Other comprehensive income (loss), net of taxes (153) (18) 161  (180) (190) Balance September 30, 2020, net of taxes $ (122) $ —  $ (4,100) $ (2,161) $ (6,383) (1) Relates to foreign currency cash flow hedges that were reclassified from AOCI to Sales. (2) Represents net realized (gains) losses on the sales of available-for-sale debt securities that were reclassified from AOCI to Other (income) expense, net. (3) Includes net amortization of prior service cost and actuarial gains and losses included in net periodic benefit cost (see Note 12).

X

- References No definition available. + Details Name: us-gaap_EquityAbstract Namespace Prefix: us-gaap_ Data Type: xbrli:stringItemType Balance Type: na Period Type: duration

X

- Definition Tabular disclosure of the components of accumulated other comprehensive income (loss). + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 30 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6450520&loc=d3e32583-110901 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=121641772&loc=SL7669686-108580 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 30 -Section 45 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=118261656&loc=d3e32211-110900 + Details Name: us-gaap_ScheduleOfAccumulatedOtherComprehensiveIncomeLossTableTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

v3.20.2

Segment Reporting (Tables)	9 Months Ended
	Sep. 30, 2020
Segment Reporting [Abstract]
Sales of Company's products	Sales of the Company’s products were as follows: Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019  ($ in millions) U.S. Int’l Total U.S. Int’l Total U.S. Int’l Total U.S. Int’l Total Pharmaceutical: Oncology Keytruda $ 2,157  $ 1,559  $ 3,715  $ 1,743  $ 1,327  $ 3,070  $ 6,106  $ 4,281  $ 10,387  $ 4,525  $ 3,448  $ 7,973  Alliance revenue - Lynparza (1) 107  89  196  71  53  123  297  223  519  186  126  313  Alliance revenue - Lenvima (1) 82  60  142  65  44  109  270  152  421  169  112  280  Emend 8  31  39  42  56  98  18  96  115  173  163  336  Vaccines Gardasil/Gardasil 9 579  608  1,187  761  558  1,320  1,209  1,732  2,941  1,579  1,464  3,044  ProQuad/M-M-R II/Varivax 437  139  576  482  141  623  1,033  356  1,390  1,325  469  1,794  Pneumovax 23 276  99  375  179  58  237  478  270  748  428  164  592  RotaTeq 114  96  210  102  78  180  355  246  601  360  203  564  Vaqta 32  19  51  36  26  62  79  60  139  103  65  167  Hospital Acute Care Bridion 162  157  320  133  151  284  412  431  843  381  437  817  Noxafil 13  66  79  77  100  177  27  220  247  268  291  560  Prevymis 32  46  77  22  23  45  87  113  200  60  55  115  Primaxin 1  73  74  2  75  77  2  187  189  2  204  207  Invanz 1  50  51  (1) 58  57  7  152  159  30  176  206  Cancidas 1  49  50  —  62  62  2  147  148  5  187  191  Cubicin 11  28  39  14  38  52  36  80  116  78  129  207  Zerbaxa 20  23  43  20  15  35  57  54  112  45  43  88  Immunology Simponi —  209  209  —  203  203  —  615  615  —  625  625  Remicade —  82  82  —  101  101  —  242  242  —  322  322  Neuroscience Belsomra 18  63  81  23  57  80  67  177  244  68  155  223  Virology Isentress/Isentress HD 92  113  205  102  149  250  243  403  646  304  449  752  Zepatier 6  22  28  24  59  83  38  83  122  96  208  304  Cardiovascular Zetia (1) 103  103  5  142  147  (4) 389  384  11  432  443  Vytorin 3  44  47  5  52  57  9  130  139  11  219  231  Atozet —  111  111  —  97  97  —  348  348  —  283  283  Alliance revenue - Adempas (2) 78  5  83  48  2  50  200  16  216  137  7  144  Adempas —  55  55  —  57  57  —  167  167  —  158  158  Diabetes Januvia 342  479  821  367  440  807  1,110  1,339  2,449  1,223  1,317  2,539  Janumet 105  400  506  129  375  503  361  1,138  1,499  462  1,105  1,567  Women’s Health Implanon/Nexplanon 137  52  189  136  62  199  374  142  515  421  160  581  NuvaRing 24  34  58  202  39  241  85  98  184  593  107  700  Diversified Brands Singulair 4  78  82  11  140  152  14  324  338  24  479  503  Cozaar/Hyzaar 5  86  91  6  110  116  17  275  292  16  313  329  Arcoxia —  68  68  —  72  72  —  204  204  —  221  221  Nasonex —  41  41  4  55  58  9  152  161  2  224  226  Follistim AQ 20  31  50  27  35  62  60  76  136  80  102  182  Other pharmaceutical (3) 352  834  1,186  343  804  1,149  1,144  2,334  3,478  1,037  2,394  3,431  Total Pharmaceutical segment sales 5,218  6,102  11,320  5,180  5,914  11,095  14,202  17,452  31,654  14,202  17,016  31,218  Animal Health: Livestock 164  594  758  144  582  726  448  1,697  2,145  406  1,601  2,007  Companion Animals 234  228  462  193  203  396  676  714  1,390  560  704  1,264  Total Animal Health segment sales 398  822  1,220  337  785  1,122  1,124  2,411  3,535  966  2,305  3,271  Other segment sales (4) —  —  —  46  —  46  23  —  23  133  1  133  Total segment sales 5,616  6,924  12,540  5,563  6,699  12,263  15,349  19,863  35,212  15,301  19,322  34,622  Other (5) 9  2  11  10  125  134  47  221  267  19  330  350    $ 5,625  $ 6,926  $ 12,551  $ 5,573  $ 6,824  $ 12,397  $ 15,396  $ 20,084  $ 35,479  $ 15,320  $ 19,652  $ 34,972  U.S. plus international may not equal total due to rounding. (1)    Alliance revenue represents Merck’s share of profits, which are product sales net of cost of sales and commercialization costs (see Note 3). (2)    Alliance revenue represents Merck’s share of profits from sales in Bayer’s marketing territories, which are product sales net of cost of sales and commercialization costs (see Note 3). (3)    Other pharmaceutical primarily reflects sales of other human health pharmaceutical products, including products within the franchises not listed separately. (4)    Represents sales for the Healthcare Services segment. All the businesses in the Healthcare Services segment were divested as of March 31, 2020. (5)    Other is primarily comprised of miscellaneous corporate revenues, including revenue hedging activities, as well as third-party manufacturing sales.
Consolidated revenues by geographic area	Consolidated sales by geographic area where derived are as follows: Three Months Ended September 30, Nine Months Ended September 30, ($ in millions) 2020 2019 2020 2019 United States $ 5,625  $ 5,573  $ 15,396  $ 15,320  Europe, Middle East and Africa 3,454  3,189  10,059  9,452  China 1,016  914  2,715  2,423  Japan 828  919  2,506  2,639  Asia Pacific (other than China and Japan) 735  756  2,129  2,217  Latin America 604  671  1,670  1,889  Other 289  375  1,004  1,032    $ 12,551  $ 12,397  $ 35,479  $ 34,972
Reconciliation of segment profits to income before taxes	A reconciliation of segment profits to Income before taxes is as follows:   Three Months Ended September 30, Nine Months Ended September 30, ($ in millions) 2020 2019 2020 2019 Segment profits: Pharmaceutical segment $ 7,974  $ 7,747  $ 22,010  $ 21,437  Animal Health segment 451  423  1,336  1,243  Other segment (1) (2) 1  (2) Total segment profits 8,424  8,168  23,347  22,678  Other profits (12) 101  188  226  Unallocated: Interest income 9  61  48  225  Interest expense (203) (231) (624) (674) Depreciation and amortization (395) (382) (1,173) (1,169) Research and development (3,272) (3,110) (7,364) (7,045) Amortization of purchase accounting adjustments (285) (329) (879) (1,105) Restructuring costs (114) (232) (269) (444) Other unallocated, net (724) (1,699) (2,490) (4,019)   $ 3,428  $ 2,347  $ 10,784  $ 8,673

X

- Definition Tabular disclosure of the reconciliation of profit (loss) from reportable segments to the consolidated income (loss) before income tax expense (benefit) and discontinued operations. Includes, but is not limited to, reconciliation after income tax if income tax is allocated to the reportable segment. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 31 -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8924-108599 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 30 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8906-108599 + Details Name: us-gaap_ReconciliationOfOperatingProfitLossFromSegmentsToConsolidatedTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

X

- Definition Tabular disclosure of entity-wide revenues from external customers for each product or service or each group of similar products or services if the information is not provided as part of the reportable operating segment information. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 40 -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9031-108599 + Details Name: us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

X

- Definition Tabular disclosure of the names of foreign countries from which revenue is material and the amount of revenue from external customers attributed to those countries. An entity may also provide subtotals of geographic information about groups of countries. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.1) -URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 41 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9038-108599 + Details Name: us-gaap_ScheduleOfRevenueFromExternalCustomersAttributedToForeignCountriesByGeographicAreaTextBlock Namespace Prefix: us-gaap_ Data Type: nonnum:textBlockItemType Balance Type: na Period Type: duration

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- References No definition available. + Details Name: us-gaap_SegmentReportingAbstract Namespace Prefix: us-gaap_ Data Type: xbrli:stringItemType Balance Type: na Period Type: duration

v3.20.2

Acquisitions, Research Collaborations and License Agreements - Acquisitions (Details) $ / shares in Units, shares in Thousands, € in Millions, $ in Millions			1 Months Ended									3 Months Ended		9 Months Ended
	Jan. 16, 2020 USD ($)	Apr. 01, 2019 USD ($)	Nov. 30, 2020 USD ($)	Oct. 31, 2020 USD ($)	Sep. 30, 2020 USD ($) $ / shares shares	Sep. 30, 2020 EUR (€)	Jul. 31, 2020 USD ($)	Jun. 30, 2020 USD ($)	May 31, 2020 USD ($)	Jul. 31, 2019 USD ($)	Apr. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) $ / shares shares	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) $ / shares shares	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Contingent consideration					$ 829.0							$ 829.0	$ 755.0	$ 829.0	$ 755.0	$ 767.0	$ 788.0
Goodwill					20,248.0							20,248.0		20,248.0		19,425.0
Research and development												3,390.0	3,204.0	7,721.0	7,324.0
Inventories					6,128.0							6,128.0		6,128.0		$ 5,978.0
Payments to Acquire Productive Assets														3,170.0	2,336.0
Forward Contracts | Research and development
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Amount of Derivative Pretax (Gain) Loss Recognized in Income												(22.0)	$ 0.0	(22.0)	$ 0.0
Forward Contracts | Research and development | Subsequent Event
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Amount of Derivative Pretax (Gain) Loss Recognized in Income				$ 6.0
Sentinel
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Payment to acquire business							$ 410.0
Dunboyne
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Other assets and liabilities, net					13.0							13.0		13.0
Payments to Acquire Productive Assets					302.0	€ 256
Property, plant and equipment					289.0							$ 289.0		$ 289.0
Themis
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Payment to acquire business								$ 366.0
Contingent consideration, maximum								740.0
Contingent consideration								97.0
IPR&D								136.0
Cash and cash equivalents								59.0
Goodwill								229.0
Deferred tax assets								71.0
Other assets and liabilities, net								(32.0)
ArQule
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Payment to acquire business	$ 2,700.0
IPR&D	2,280.0
Share-based compensation payments attributable to precombination service	138.0
Transaction costs	95.0
Cash and cash equivalents	145.0
Goodwill	540.0
Other assets and liabilities, net	34.0
Deferred income tax liabilities	389.0
Intangible assets	$ 80.0
Peloton
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Payment to acquire business										$ 1,200.0
Cash and cash equivalents										157.0
Other assets and liabilities, net										6.0
Research and development										982.0
Deferred income tax liabilities										64.0
Antelliq
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Payment to acquire business		$ 2,300.0
Transaction costs		47.0
Cash and cash equivalents		31.0
Goodwill		1,376.0
Debt assumed and paid		1,300.0
Other assets and liabilities, net		(82.0)
Deferred income tax liabilities		589.0
Inventories		93.0
Intangible assets		2,689.0
Property, plant and equipment		$ 60.0
Immune Design
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Payment to acquire business											$ 301.0
IPR&D											156.0
Cash and cash equivalents											83.0
Other net assets											42.0
Goodwill											$ 20.0
VelosBio [Member] | Forecast
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Payment to acquire business			$ 2,750.0
Development Milestones | Themis
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Contingent consideration, maximum								80.0
Sales-Based Milestones | Themis
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Contingent consideration, maximum								400.0
Sales-Based Milestones | Peloton
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Contingent consideration, maximum										1,050.0
Regulatory Milestones | Themis
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Contingent consideration, maximum								$ 260.0
Regulatory Milestones | Peloton
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Contingent consideration, maximum										50.0
Commercial Milestone | Peloton
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Contingent consideration, maximum										$ 50.0
Seagen
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Upfront and milestone payments					$ 600.0
Share price (in dollars per share) | $ / shares					$ 200							$ 200		$ 200
Contingent milestone payments collaborative arrangement					$ 2,600.0
Payments to Acquire Investments					1,000.0
Research and development					$ 622.0
Forward contract, shares | shares					5,000							5,000		5,000
Seagen | Tukysa
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Upfront and milestone payments					$ 210.0
Seagen | Tukysa | Minimum
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Royalty Rate, Percentage					20.00%	20.00%
Seagen | Tukysa | Maximum
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Royalty Rate, Percentage					33.00%	33.00%
Seagen | Sales-Based Milestones
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Contingent milestone payments collaborative arrangement					$ 1,750.0
Seagen | Regulatory Milestones
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Contingent milestone payments collaborative arrangement					850.0
Seagen | Regulatory Milestones | Tukysa
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Contingent milestone payments collaborative arrangement					$ 65.0
IAVI
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Upfront and milestone payments									$ 6.5
Contingent milestone payments collaborative arrangement									$ 100.0
Technology Rights | Sentinel
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Acquired rights							401.0
Inventories							$ 9.0

X

- Definition Business Combination, Recognized Identifiable Assets Acquired (Liabilities) Assumed, Other Assets And Liabilities, Net + References No definition available. + Details Name: mrk_BusinessCombinationRecognizedIdentifiableAssetsAcquiredLiabilitiesAssumedOtherAssetsAndLiabilitiesNet Namespace Prefix: mrk_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: instant

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- Definition Represents payments that may be made in the future contingent upon the achievement of regulatory and/or sales milestones as part of a collaborative arrangement. + References No definition available. + Details Name: mrk_ContingentPaymentsCollaborativeArrangement Namespace Prefix: mrk_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: duration

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v3.20.2

Acquisitions, Research Collaborations and License Agreements - Fair Value of Assets Acquired and Liabilities Assumed (Details) $ in Millions		1 Months Ended
	Apr. 01, 2019 USD ($)	Jul. 31, 2020	Sep. 30, 2020 USD ($)	Jan. 16, 2020 USD ($)	Dec. 31, 2019 USD ($)
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Goodwill			$ 20,248		$ 19,425
Sentinel | Technology Rights
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Weighted average useful life of acquired finite-lived intangible assets		15 years
Antelliq | Technology Rights | Minimum
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Weighted average useful life of acquired finite-lived intangible assets	18 years
Antelliq | Technology Rights | Maximum
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Weighted average useful life of acquired finite-lived intangible assets	24 years
ArQule
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Cash and cash equivalents				$ 145
IPR&D				2,280
Intangible assets				80
Deferred income tax liabilities				(389)
Other assets and liabilities, net				34
Total identifiable net assets				2,150
Goodwill				540
Consideration transferred				$ 2,690
Antelliq
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Cash and cash equivalents	$ 31
Accounts receivable	73
Inventories	93
Property, plant and equipment	60
Intangible assets	2,689
Deferred income tax liabilities	(589)
Other assets and liabilities, net	(82)
Total identifiable net assets	2,275
Goodwill	1,376
Consideration transferred	$ 3,651
Measurement Input, Discount Rate | ArQule
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Present value discount rate				0.125
Measurement Input, Discount Rate | Antelliq
Acquisitions Research Collaborations And License Agreements Transactions [Line Items]
Present value discount rate	0.115

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v3.20.2

Collaborative Arrangements - Narrative (Details) - USD ($) $ in Millions	1 Months Ended					3 Months Ended			9 Months Ended		12 Months Ended		21 Months Ended	29 Months Ended	37 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018	Jul. 31, 2017	Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2019	Mar. 31, 2021
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Research and development						$ 3,390		$ 3,204	$ 7,721	$ 7,324
Other liabilities, noncurrent						12,027			12,027		$ 11,970		$ 11,970	$ 11,970
Lynparza | Other Assets
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Finite-lived intangible assets						1,300			1,300
Lenvima | Other Assets
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Finite-lived intangible assets						1,100			1,100
Adempas | Other intangible assets
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Finite-lived intangible assets						$ 838			838
AstraZeneca
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront and milestone payments					$ 1,600
License option payment related to collaborative arrangement					$ 750
AstraZeneca | Sales-Based Milestones
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Contingent milestone payments collaborative arrangement									2,700
AstraZeneca | Sales-Based Milestones | Lynparza
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Probable contingent payments collaborative arrangement							$ 400							$ 1,000
Liabilities							400
Milestone payments made to collaborative partner									250		200	$ 250
AstraZeneca | Regulatory Milestones | Lynparza
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestone payments made to collaborative partner							135				60	140
Contingent milestone payments collaborative arrangement									1,400
Eisai
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront and milestone payments				$ 750
License option payment related to collaborative arrangement		$ 200	$ 325
Eisai | Forecast
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
License option payment related to collaborative arrangement	$ 125														$ 650
Eisai | Sales-Based Milestones
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Contingent milestone payments collaborative arrangement									2,700
Eisai | Sales-Based Milestones | Lenvima
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Probable contingent payments collaborative arrangement							370						$ 950
Liabilities							$ 370
Milestone payments made to collaborative partner									500		50
Eisai | Regulatory Milestones
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Contingent milestone payments collaborative arrangement									135
Eisai | Regulatory Milestones | Lenvima
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestone payments made to collaborative partner												250
Bayer AG | Sales-Based Milestones
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Probable contingent payments collaborative arrangement											$ 725
Milestone payments made to collaborative partner												$ 350
Contingent milestone payments collaborative arrangement									$ 400

X

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- Definition Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 926 -SubTopic 20 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=120154696&loc=d3e54445-107959 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275 + Details Name: us-gaap_FiniteLivedIntangibleAssetsNet Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: instant

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- Definition Sum of the carrying amounts as of the balance sheet date of all liabilities that are recognized. Liabilities are probable future sacrifices of economic benefits arising from present obligations of an entity to transfer assets or provide services to other entities in the future. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 45 -Paragraph 25 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=116870748&loc=SL6758485-165988 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 28 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=75031198&loc=d3e14064-108612 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (bb) -URI http://asc.fasb.org/extlink&oid=121559654&loc=d3e5710-111685 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19-26) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=121559654&loc=d3e5710-111685 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571 Reference 7: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 30 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8906-108599 Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08(g)(1)(ii)) -URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690 + Details Name: us-gaap_Liabilities Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: instant

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v3.20.2

Collaborative Arrangements - Schedule of Transactions (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Sales	$ 12,551	$ 12,397	$ 35,479	$ 34,972
Cost of sales	3,481	3,990	9,952	10,443
Selling, general and administrative	2,450	2,589	7,383	7,726
Research and development	3,390	3,204	7,721	7,324
Payables, current	20,405		20,405		$ 22,220
Other current assets | AstraZeneca | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Receivables	197		197		128
Other current assets | Eisai | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Receivables	170		170		150
Other current assets | Bayer AG | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Receivables	70		70		49
Accounts payable and accrued liabilities | AstraZeneca | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Payables, current	309		309		577
Payables, Noncurrent	400		400		0
Accounts payable and accrued liabilities | Eisai | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Payables, current	325		325		700
Other Noncurrent Liabilities | Eisai | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Payables, Noncurrent	570		570		525
Other Noncurrent Liabilities | Bayer AG | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Payables, Noncurrent	375		375		$ 375
Revenue | AstraZeneca | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Alliance revenue - profit sharing	199	123	522	313
Revenue | AstraZeneca | Collaborative Arrangement | Alliance revenue - Lynparza (1)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Alliance revenue - profit sharing	196	123	519	313
Revenue | AstraZeneca | Collaborative Arrangement | Alliance revenue - Koselugo
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Alliance revenue - profit sharing	3	0	3	0
Revenue | Eisai | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Alliance revenue - profit sharing	142	109	421	280
Revenue | Bayer AG | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Alliance revenue - profit sharing	83	50	216	144
Collaborative Arrangement, Sales, Net	55	57	167	158
Sales	138	107	383	302
Cost of sales | AstraZeneca | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Cost of sales	41	28	205	120
Cost of sales | Eisai | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Cost of sales	46	23	215	97
Cost of sales | Bayer AG | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Cost of sales	29	28	85	86
Selling, general and administrative | AstraZeneca | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Selling, general and administrative	40	36	112	96
Selling, general and administrative | Eisai | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Selling, general and administrative	18	21	48	59
Selling, general and administrative | Bayer AG | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Selling, general and administrative	19	12	42	31
Research and development | AstraZeneca | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Research and development	20	44	93	122
Research and development | Eisai | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Research and development	48	37	168	146
Research and development | Bayer AG | Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Research and development	$ 12	$ 31	$ 53	$ 94

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- Definition The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 985 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6501960&loc=d3e128462-111756 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 730 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6420194&loc=d3e21568-108373 + Details Name: us-gaap_ResearchAndDevelopmentExpense Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: duration

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v3.20.2

Restructuring - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2020
Restructuring Cost and Reserve [Line Items]
Cumulative costs since program inception	$ 1,400		$ 1,400
Estimate of cumulative pre tax costs that will result in cash outlays			60.00%
Estimate of cumulative pre tax costs that will be noncash			40.00%
Expected restructuring and related cost	2,500		$ 2,500
Total pretax restructuring costs	$ 186	$ 296	$ 504	$ 642
Forecast
Restructuring Cost and Reserve [Line Items]
Expected restructuring and related cost					$ 800

X

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v3.20.2

Restructuring - Charges Activities by Type of Cost (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	$ 186	$ 296	$ 504	$ 642
Separation Costs
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	61	205	143	358
Accelerated Depreciation
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	66	41	192	173
Other
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	59	50	169	111
Cost of sales
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	38	62	131	161
Cost of sales | Separation Costs
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	0	0	0	0
Cost of sales | Accelerated Depreciation
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	33	41	89	139
Cost of sales | Other
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	5	21	42	22
Selling, general and administrative
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	15	1	37	33
Selling, general and administrative | Separation Costs
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	0	0	0	0
Selling, general and administrative | Accelerated Depreciation
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	15	1	37	33
Selling, general and administrative | Other
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	0	0	0	0
Research and development
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	19	1	67	4
Research and development | Separation Costs
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	0	0	0	0
Research and development | Accelerated Depreciation
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	18	(1)	66	1
Research and development | Other
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	1	2	1	3
Restructuring costs
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	114	232	269	444
Restructuring costs | Separation Costs
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	61	205	143	358
Restructuring costs | Accelerated Depreciation
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	0	0	0	0
Restructuring costs | Other
Restructuring Cost and Reserve [Line Items]
Total pretax restructuring costs	$ 53	$ 27	$ 126	$ 86

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- Details Name: us-gaap_IncomeStatementLocationAxis=us-gaap_RestructuringChargesMember Namespace Prefix: Data Type: na Balance Type: Period Type:

v3.20.2

Restructuring - Activities by Program (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance			$ 759
Expense	$ 186	$ 296	504	$ 642
(Payments) receipts, net			(632)
Non-cash activity			(153)
Restructuring reserve, ending balance	478		478
Separation Costs
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance			690
Expense	61	205	143	358
(Payments) receipts, net			(395)
Non-cash activity			0
Restructuring reserve, ending balance	438		438
Accelerated Depreciation
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance			0
Expense	66	41	192	173
(Payments) receipts, net			0
Non-cash activity			(192)
Restructuring reserve, ending balance	0		0
Other
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance			69
Expense	59	$ 50	169	$ 111
(Payments) receipts, net			(237)
Non-cash activity			39
Restructuring reserve, ending balance	$ 40		$ 40

X

- Definition Noncash activity affecting the restructuring reserve, including accelerated depreciation. + References No definition available. + Details Name: mrk_RestructuringReserveNoncashActivity Namespace Prefix: mrk_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: duration

X

- Definition Amount of cash payments made as the result of exit or disposal activities. Excludes payments associated with a discontinued operation or an asset retirement obligation. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b)(2) -URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 17 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3367-108585 + Details Name: us-gaap_PaymentsForRestructuring Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: duration

X

- Definition Discloses the amount charged against the accrued restructuring reserves, or earnings if not previously accrued, during the period for the specified type of restructuring cost. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SAB Topic 5.P.4(b)(1)) -URI http://asc.fasb.org/extlink&oid=115931487&loc=d3e140904-122747 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SAB Topic 5.P.4(d)) -URI http://asc.fasb.org/extlink&oid=115931487&loc=d3e140904-122747 + Details Name: us-gaap_RestructuringAndRelatedCostIncurredCost Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: duration

X

- Definition Carrying amount (including both current and noncurrent portions of the accrual) as of the balance sheet date pertaining to a specified type of cost associated with exit from or disposal of business activities or restructuring pursuant to a duly authorized plan. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b)(2) -URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SAB TOPIC 5.P.4(b)) -URI http://asc.fasb.org/extlink&oid=115931487&loc=d3e140904-122747 + Details Name: us-gaap_RestructuringReserve Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: instant

X

- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details Name: us-gaap_RestructuringReserveRollForward Namespace Prefix: us-gaap_ Data Type: xbrli:stringItemType Balance Type: na Period Type: duration

X

- Details Name: us-gaap_RestructuringCostAndReserveAxis=us-gaap_OneTimeTerminationBenefitsMember Namespace Prefix: Data Type: na Balance Type: Period Type:

X

- Details Name: us-gaap_RestructuringCostAndReserveAxis=mrk_AcceleratedDepreciationMember Namespace Prefix: Data Type: na Balance Type: Period Type:

X

- Details Name: us-gaap_RestructuringCostAndReserveAxis=us-gaap_OtherRestructuringMember Namespace Prefix: Data Type: na Balance Type: Period Type:

v3.20.2

Financial Instruments - Narrative (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($) interest_rate_swap	Dec. 31, 2019 USD ($)	Sep. 30, 2020 USD ($) interest_rate_swap	Sep. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)	Feb. 29, 2020 USD ($) interest_rate_swap
Derivative [Line Items]
Pretax net unrealized losses on derivatives maturing within next 12 months estimated to be reclassified from AOCI to sales			$ 155,000,000
Equity investments without readily determinable fair values	$ 508,000,000		508,000,000	$ 393,000,000
Unrealized gains recognized on investments in equity securities without readily determinable fair value			21,000,000	4,000,000
Unrealized losses recognized on investments in equity securities without readily determinable fair values			3,000,000	12,000,000
Cumulative unrealized gains on investments	128,000,000		128,000,000
Cumulative unrealized losses on investments	24,000,000		24,000,000
Payments of contingent consideration			106,000,000	$ 85,000,000
Fair value of loans payable and long-term debt, including current portion	32,600,000,000	$ 28,800,000,000	32,600,000,000
Debt, carrying amount	28,700,000,000	26,300,000,000	28,700,000,000
Accounts Receivable, Sale	2,100,000,000	2,700,000,000
Cash collateral received from counterparties	0	34,000,000	0
Cash collateral advanced to counterparties	0	0	0
Total swap notional amount	27,151,000,000	30,666,000,000	27,151,000,000
Face amount of debt					$ 4,500,000,000
Level 2
Derivative [Line Items]
Cash equivalents	6,600,000,000	8,900,000,000	6,600,000,000
Derivatives Designated as Hedging Instruments
Derivative [Line Items]
Total swap notional amount	12,654,000,000	14,728,000,000	$ 12,654,000,000
Derivatives Designated as Hedging Instruments | Maximum
Derivative [Line Items]
Maximum average period of maturities of contracts in years (less than)			2 years
Derivatives Not Designated as Hedging Instruments
Derivative [Line Items]
Total swap notional amount	$ 14,497,000,000	$ 15,938,000,000	$ 14,497,000,000
Derivatives Not Designated as Hedging Instruments | Maximum
Derivative [Line Items]
Maximum average period of maturities of contracts in years (less than)			1 year
1.85% Notes Due 2020
Derivative [Line Items]
Face amount of debt						$ 1,250,000,000
Stated interest rate (as percent)						1.85%
Interest rate swap contracts
Derivative [Line Items]
Number of interest rate swaps held (in interest rate swaps) | interest_rate_swap	14		14			5
Total swap notional amount						$ 250,000,000

X

- Definition Amount of decrease from sale of accounts receivable. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 11 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919244-210447 + Details Name: us-gaap_AccountsReceivableSale Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: duration

X

- Definition Amount of short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.1) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details Name: us-gaap_CashEquivalentsAtCarryingValue Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: instant

X

- Definition Face (par) amount of debt instrument at time of issuance. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28551-108399 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400 + Details Name: us-gaap_DebtInstrumentFaceAmount Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: instant

X

- Definition Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=121572278&loc=d3e13433-108611 + Details Name: us-gaap_DebtInstrumentFairValue Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: instant

X

- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details Name: us-gaap_DebtInstrumentInterestRateStatedPercentage Namespace Prefix: us-gaap_ Data Type: num:percentItemType Balance Type: na Period Type: instant

X

- Definition Represents the aggregate of total long-term debt, including current maturities and short-term debt. + References No definition available. + Details Name: us-gaap_DebtLongtermAndShorttermCombinedAmount Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: instant

X

- Definition Average remaining period until maturity of the derivative contract, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details Name: us-gaap_DerivativeAverageRemainingMaturity1 Namespace Prefix: us-gaap_ Data Type: xbrli:durationItemType Balance Type: na Period Type: duration

X

- Definition Amount of obligation to return cash collateral under master netting arrangements that have not been offset against derivative assets. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226016-175313 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 8 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121590274&loc=d3e41678-113959 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 + Details Name: us-gaap_DerivativeCollateralObligationToReturnCash Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: instant

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- Definition Amount of right to receive cash collateral under master netting arrangements that have not been offset against derivative liabilities. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226016-175313 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 8 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121590274&loc=d3e41678-113959 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 + Details Name: us-gaap_DerivativeCollateralRightToReclaimCash Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: instant

X

- Definition The estimated value of gains (losses), net anticipated to be transferred in the future from accumulated other comprehensive income into earnings. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 30 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=121549185&loc=d3e80845-113994 + Details Name: us-gaap_DerivativeInstrumentsGainLossReclassificationFromAccumulatedOCIToIncomeEstimatedNetAmountToBeTransferred Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: duration

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details Name: us-gaap_DerivativeLineItems Namespace Prefix: us-gaap_ Data Type: xbrli:stringItemType Balance Type: na Period Type: duration

X

- Definition Nominal or face amount used to calculate payment on derivative. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5580258-113959 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5579245-113959 + Details Name: us-gaap_DerivativeNotionalAmount Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: na Period Type: instant

X

- Definition Amount of investment in equity security without readily determinable fair value. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 321 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=120269885&loc=SL75117539-209714 + Details Name: us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: instant

X

- Definition Amount of loss from downward price adjustment on investment in equity security without readily determinable fair value. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 321 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=120269885&loc=SL75117539-209714 + Details Name: us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueDownwardPriceAdjustmentAnnualAmount Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: duration

X

- Definition Amount of cumulative loss from downward price adjustment on investment in equity security without readily determinable fair value. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 321 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=120269885&loc=SL75117539-209714 + Details Name: us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueDownwardPriceAdjustmentCumulativeAmount Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: instant

X

- Definition Amount of gain from upward price adjustment on investment in equity security without readily determinable fair value. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 321 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=120269885&loc=SL75117539-209714 + Details Name: us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentAnnualAmount Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: duration

X

- Definition Amount of cumulative gain from upward price adjustment on investment in equity security without readily determinable fair value. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 321 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=120269885&loc=SL75117539-209714 + Details Name: us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueUpwardPriceAdjustmentCumulativeAmount Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: instant

X

- Definition Amount of settlements of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details Name: us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: duration

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- Definition Number of interest rate derivative instruments held by the entity at the reporting date. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5579245-113959 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5580258-113959 + Details Name: us-gaap_NumberOfInterestRateDerivativesHeld Namespace Prefix: us-gaap_ Data Type: xbrli:integerItemType Balance Type: na Period Type: instant

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v3.20.2

Financial Instruments - Effect of Net Investment Hedges (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Pretax (Gain) Loss Recognized in Other Comprehensive Income	$ 10	$ 1	$ 15	$ 8
Foreign exchange contracts | Other (income) expense, net
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Pretax (Gain) Loss Recognized in Other (income) expense, net for Amounts Excluded from Effectiveness Testing	(4)	(8)	(15)	(23)
Euro-denominated notes
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Pretax (Gain) Loss Recognized in Other Comprehensive Income	162	(150)	182	(152)
Euro-denominated notes | Other (income) expense, net
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Pretax (Gain) Loss Recognized in Other (income) expense, net for Amounts Excluded from Effectiveness Testing	$ 0	$ 0	$ 0	$ 0

X

- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details Name: us-gaap_DerivativeInstrumentsGainLossLineItems Namespace Prefix: us-gaap_ Data Type: xbrli:stringItemType Balance Type: na Period Type: duration

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- Definition Amount, before tax and reclassification, of gain (loss) from derivative designated and qualifying as net investment hedge. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4CCC -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL109998896-113959 + Details Name: us-gaap_OtherComprehensiveIncomeLossNetInvestmentHedgeGainLossBeforeReclassificationAndTax Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: duration

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- Definition Amount, before tax, of reclassification from accumulated other comprehensive income (AOCI) for gain (loss) from derivative designated and qualifying as net investment hedge. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4CCC -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL109998896-113959 + Details Name: us-gaap_OtherComprehensiveIncomeLossNetInvestmentHedgeGainLossReclassificationBeforeTax Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: duration

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- Details Name: us-gaap_DerivativeInstrumentRiskAxis=mrk_EurodominatedNotesMember Namespace Prefix: Data Type: na Balance Type: Period Type:

v3.20.2

Financial Instruments - Summary of Interest Rate Swaps Held (Details)	Sep. 30, 2020 USD ($) interest_rate_swap	Jun. 30, 2020 USD ($)	Feb. 29, 2020 USD ($) interest_rate_swap	Dec. 31, 2019 USD ($)
Derivative [Line Items]
Par Value of Debt		$ 4,500,000,000
Total swap notional amount	$ 27,151,000,000			$ 30,666,000,000
Interest rate swap contracts
Derivative [Line Items]
Number of Interest Rate Swaps Held (in interest rate swaps) | interest_rate_swap	14		5
Total swap notional amount			$ 250,000,000
3.875% notes due 2021 | Interest rate swap contracts
Derivative [Line Items]
Stated interest rate (as percent)	3.875%
Par Value of Debt	$ 1,150,000,000
Number of Interest Rate Swaps Held (in interest rate swaps) | interest_rate_swap	5
Total swap notional amount	$ 1,150,000,000
2.40% notes due 2022 | Interest rate swap contracts
Derivative [Line Items]
Stated interest rate (as percent)	2.40%
Par Value of Debt	$ 1,000,000,000
Number of Interest Rate Swaps Held (in interest rate swaps) | interest_rate_swap	4
Total swap notional amount	$ 1,000,000,000
2.35% notes due 2022 | Interest rate swap contracts
Derivative [Line Items]
Stated interest rate (as percent)	2.35%
Par Value of Debt	$ 1,250,000,000
Number of Interest Rate Swaps Held (in interest rate swaps) | interest_rate_swap	5
Total swap notional amount	$ 1,250,000,000

X

- Definition Face (par) amount of debt instrument at time of issuance. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28551-108399 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400 + Details Name: us-gaap_DebtInstrumentFaceAmount Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: instant

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- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details Name: us-gaap_DebtInstrumentInterestRateStatedPercentage Namespace Prefix: us-gaap_ Data Type: num:percentItemType Balance Type: na Period Type: instant

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details Name: us-gaap_DerivativeLineItems Namespace Prefix: us-gaap_ Data Type: xbrli:stringItemType Balance Type: na Period Type: duration

X

- Definition Nominal or face amount used to calculate payment on derivative. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5580258-113959 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5579245-113959 + Details Name: us-gaap_DerivativeNotionalAmount Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: na Period Type: instant

X

- Definition Number of interest rate derivative instruments held by the entity at the reporting date. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5579245-113959 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5580258-113959 + Details Name: us-gaap_NumberOfInterestRateDerivativesHeld Namespace Prefix: us-gaap_ Data Type: xbrli:integerItemType Balance Type: na Period Type: instant

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- Details Name: us-gaap_LongtermDebtTypeAxis=mrk_A2.35NotesDue2022Member Namespace Prefix: Data Type: na Balance Type: Period Type:

v3.20.2

Financial Instruments - Fair Value Hedges (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Loans payable and current portion of long-term debt
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Carrying Amount of Hedged Liabilities	$ 1,155	$ 1,249
Cumulative Amount of Fair Value Hedging Adjustment Increase (Decrease) Included in the Carrying Amount	5	(1)
Long-Term Debt
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Carrying Amount of Hedged Liabilities	2,309	3,409
Cumulative Amount of Fair Value Hedging Adjustment Increase (Decrease) Included in the Carrying Amount	$ 62	$ 14

X

- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details Name: us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems Namespace Prefix: us-gaap_ Data Type: xbrli:stringItemType Balance Type: na Period Type: duration

X

- Definition Amount of liability hedged in fair value hedging relationship. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4EE -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL109999712-113959 + Details Name: us-gaap_HedgedLiabilityFairValueHedge Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: instant

X

- Definition Amount of cumulative increase (decrease) in fair value of hedged liability in fair value hedge, attributable to hedged risk. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4EE -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL109999712-113959 + Details Name: us-gaap_HedgedLiabilityFairValueHedgeCumulativeIncreaseDecrease Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: instant

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- Details Name: us-gaap_BalanceSheetLocationAxis=mrk_LongTermDebtCurrentMaturitiesMember Namespace Prefix: Data Type: na Balance Type: Period Type:

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- Details Name: us-gaap_BalanceSheetLocationAxis=mrk_LongTermDebtExcludingCurrentMaturitiesMember Namespace Prefix: Data Type: na Balance Type: Period Type:

v3.20.2

Financial Instruments - Fair Value of Derivatives Segregated between those Derivatives that are Designated as Hedging Instruments and those that are Not Designated as Hedging Instruments (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Asset	$ 239	$ 288
Fair Value of Derivative, Liability	298	97
U.S Dollar Notional Amount	27,151	30,666
Derivatives Designated as Hedging Instruments
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Asset	158	222
Fair Value of Derivative, Liability	105	24
U.S Dollar Notional Amount	12,654	14,728
Derivatives Not Designated as Hedging Instruments
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Asset	81	66
Fair Value of Derivative, Liability	193	73
U.S Dollar Notional Amount	14,497	15,938
Interest rate swap contracts | Derivatives Designated as Hedging Instruments | Other current assets
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Asset	6	0
U.S Dollar Notional Amount	1,150	0
Interest rate swap contracts | Derivatives Designated as Hedging Instruments | Other Assets
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Asset	63	15
U.S Dollar Notional Amount	2,250	3,400
Interest rate swap contracts | Derivatives Designated as Hedging Instruments | Accrued and other current liabilities
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Liability	0	1
U.S Dollar Notional Amount	0	1,250
Foreign exchange contracts | Derivatives Designated as Hedging Instruments | Other current assets
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Asset	30	152
U.S Dollar Notional Amount	4,120	6,117
Foreign exchange contracts | Derivatives Designated as Hedging Instruments | Other Assets
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Asset	59	55
U.S Dollar Notional Amount	1,881	2,160
Foreign exchange contracts | Derivatives Designated as Hedging Instruments | Accrued and other current liabilities
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Liability	104	22
U.S Dollar Notional Amount	3,096	1,748
Foreign exchange contracts | Derivatives Designated as Hedging Instruments | Other Noncurrent Liabilities
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Liability	1	1
U.S Dollar Notional Amount	157	53
Foreign exchange contracts | Derivatives Not Designated as Hedging Instruments | Other current assets
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Asset	81	66
U.S Dollar Notional Amount	5,455	7,245
Foreign exchange contracts | Derivatives Not Designated as Hedging Instruments | Accrued and other current liabilities
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Liability	171	73
U.S Dollar Notional Amount	8,042	8,693
Forward Contracts | Derivatives Not Designated as Hedging Instruments | Accrued and other current liabilities
Derivatives, Fair Value [Line Items]
Fair Value of Derivative, Liability	22	0
U.S Dollar Notional Amount	$ 1,000	$ 0

X

- Definition Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=121572278&loc=d3e13433-108611 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 + Details Name: us-gaap_DerivativeAssets Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: instant

X

- Definition Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=121572278&loc=d3e13433-108611 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313 + Details Name: us-gaap_DerivativeLiabilities Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: instant

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- Definition Nominal or face amount used to calculate payment on derivative. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1B -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5580258-113959 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5579245-113959 + Details Name: us-gaap_DerivativeNotionalAmount Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: na Period Type: instant

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details Name: us-gaap_DerivativesFairValueLineItems Namespace Prefix: us-gaap_ Data Type: xbrli:stringItemType Balance Type: na Period Type: duration

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v3.20.2

Financial Instruments - Information on Derivative Positions Subject to Master Netting Arrangements as if they were Presented on a Net Basis (Details) - USD ($)	Sep. 30, 2020	Dec. 31, 2019
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Gross amounts recognized in the consolidated balance sheet, asset	$ 239,000,000	$ 288,000,000
Gross amount subject to offset in master netting arrangements not offset in the condensed balance sheet, asset	(140,000,000)	(84,000,000)
Cash collateral received, asset	0	(34,000,000)
Net amounts, asset	99,000,000	170,000,000
Gross amounts recognized in the consolidated balance sheet, liability	298,000,000	97,000,000
Gross amount subject to offset in master netting arrangements not offset in the condensed balance sheet, liability	(140,000,000)	(84,000,000)
Cash collateral received, liability	0	0
Net amounts, liability	$ 158,000,000	$ 13,000,000

X

- Definition Fair value, after effects of master netting arrangements, deduction of assets not subject to a master netting arrangement and elected not to be offset, of financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, offset against an obligation to return collateral. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226016-175313 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 + Details Name: us-gaap_DerivativeAssetFairValueOffsetAgainstCollateralNetOfNotSubjectToMasterNettingArrangementPolicyElection Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: instant

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- Definition Fair value of financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, elected not to be offset, deducted from derivative assets. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226016-175313 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (d)(1)(i) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 + Details Name: us-gaap_DerivativeAssetNotOffsetPolicyElectionDeduction Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: instant

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- Definition Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=121572278&loc=d3e13433-108611 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 + Details Name: us-gaap_DerivativeAssets Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: instant

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- Definition Amount of obligation to return cash collateral under master netting arrangements that have not been offset against derivative assets. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226016-175313 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 8 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121590274&loc=d3e41678-113959 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 + Details Name: us-gaap_DerivativeCollateralObligationToReturnCash Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: instant

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- Definition Amount of right to receive cash collateral under master netting arrangements that have not been offset against derivative liabilities. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226016-175313 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 8 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121590274&loc=d3e41678-113959 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 + Details Name: us-gaap_DerivativeCollateralRightToReclaimCash Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: instant

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- Definition Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=121572278&loc=d3e13433-108611 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313 + Details Name: us-gaap_DerivativeLiabilities Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: instant

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- Definition Fair value, after effects of master netting arrangements, deduction of liabilities not subject to a master netting arrangement and elected not to be offset, of financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, offset against the right to receive collateral. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226016-175313 + Details Name: us-gaap_DerivativeLiabilityFairValueOffsetAgainstCollateralNetOfNotSubjectToMasterNettingArrangementPolicyElection Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: instant

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- Definition Fair value of financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, elected not to be offset, deducted from derivative liabilities. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (d)(1)(i) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226016-175313 + Details Name: us-gaap_DerivativeLiabilityNotOffsetPolicyElectionDeduction Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: instant

v3.20.2

Financial Instruments - Location and Amount of Pretax (Gains) Losses of Derivatives (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Sales	$ 12,551	$ 12,397	$ 35,479	$ 34,972
Other (income) expense, net	(312)	35	(630)	362
Other comprehensive income (loss)	10	(28)	(190)	155
Interest rate swap contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amount of (loss) gain recognized in OCI on derivatives	(1)	(1)	(3)	(6)
Interest rate swap contracts | Other (income) expense, net
Derivative Instruments, Gain (Loss) [Line Items]
Hedged items	(14)	13	54	101
Derivatives designated as hedging instruments	0	(6)	(76)	(74)
Amount of gain recognized in Other (income) expense, net on derivatives	(1)	(1)	(3)	(3)
Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Amount of (loss) gain recognized in OCI on derivatives	(195)	186	(126)	183
Increase (decrease) in Sales as a result of AOCI reclassifications	23	(70)	(65)	(189)
Foreign exchange contracts | Reclassification out of Accumulated Other Comprehensive Income | Accumulated Gain (Loss), Cash Flow Hedge, Including Noncontrolling Interest
Derivative Instruments, Gain (Loss) [Line Items]
Sales	$ (23)	$ 70	$ 65	$ 189

X

- Definition Amount of gain (loss) from the increase (decrease) in fair value of derivative and nonderivative instruments designated as fair value hedging instruments recognized in the income statement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 25 -Section 50 -Paragraph 1 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=121577467&loc=d3e76258-113986 + Details Name: us-gaap_ChangeInUnrealizedGainLossOnFairValueHedgingInstruments1 Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: duration

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- Definition Amount of the increase (decrease) in fair value of the hedged item in a fair value hedge recognized in the income statement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 25 -Section 50 -Paragraph 1 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=121577467&loc=d3e76258-113986 + Details Name: us-gaap_ChangeInUnrealizedGainLossOnHedgedItemInFairValueHedge1 Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: duration

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- Definition Amount of increase (decrease) in the fair value of derivatives recognized in the income statement. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5618551-113959 + Details Name: us-gaap_DerivativeGainLossOnDerivativeNet Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: duration

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- Definition Amount, before tax and reclassification, of gain (loss) from derivative instrument designated and qualifying cash flow hedge included in assessment of hedge effectiveness. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 20 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=121577181&loc=SL110061190-113977 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4A -Subparagraph (b)(2) -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5618551-113959 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5624171-113959 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=121641772&loc=d3e637-108580 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=121641772&loc=SL7669646-108580 + Details Name: us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: duration

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- Definition Amount, after tax, of reclassification of gain (loss) from accumulated other comprehensive income (AOCI) for derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=121641772&loc=d3e689-108580 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=121641772&loc=d3e637-108580 + Details Name: us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: duration

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- Definition Amount after tax of other comprehensive income (loss) attributable to parent entity. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 1B -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121641772&loc=SL7669625-108580 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=109239629&loc=SL4573702-111684 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 45 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=108774443&loc=SL4569643-111683 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 1A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121641772&loc=SL7669619-108580 Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 45 -Paragraph 19 -URI http://asc.fasb.org/extlink&oid=108774443&loc=SL4569616-111683 + Details Name: us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: duration

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- Definition Amount of income (expense) related to nonoperating activities, classified as other. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.9) -URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227 + Details Name: us-gaap_OtherNonoperatingIncomeExpense Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: duration

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- Definition Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 22 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8736-108599 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 28 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=75031198&loc=d3e14064-108612 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 32 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 32 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 22 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8736-108599 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 40 -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9031-108599 Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 30 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8906-108599 Reference 9: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 41 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9038-108599 Reference 10: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 42 -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9054-108599 Reference 11: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08(g)(1)(ii)) -URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690 Reference 12: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 235 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-05(b)(2)) -URI http://asc.fasb.org/extlink&oid=120399901&loc=d3e537907-122884 Reference 13: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03(1)) -URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227 + Details Name: us-gaap_Revenues Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: duration

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v3.20.2

Financial Instruments - Income Statement Effects on Derivatives Not Designated as Hedging Instruments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Foreign currency | Other (income) expense, net
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Derivative Pretax (Gain) Loss Recognized in Income	$ (7)	$ (8)	$ (138)	$ 112
Forecasted transactions | Sales
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Derivative Pretax (Gain) Loss Recognized in Income	7	(11)	4	(7)
Treasury lock | Other (income) expense, net
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Derivative Pretax (Gain) Loss Recognized in Income	0	0	9	0
Forward Contracts | Research and development
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Derivative Pretax (Gain) Loss Recognized in Income	$ 22	$ 0	$ 22	$ 0

X

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- Definition Amount of realized and unrealized gain (loss) of derivative instruments not designated or qualifying as hedging instruments. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4CC -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL109998890-113959 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4C -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5624171-113959 + Details Name: us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsGainLossNet Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: duration

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v3.20.2

Financial Instruments - Information on Available-for-sale Investments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Debt securities, amortized cost	$ 76		$ 76		$ 1,768
Debt securities, unrealized gains	0		0		17
Debt securities, unrealized losses	0		0		0
Debt securities, fair value	76		76		1,785
Publicly traded equity securities, fair value	1,477		1,477		838
Total debt and publicly traded equity securities, fair value	1,553		1,553		2,623
Unrealized net losses (gains)	(43)	$ 25	(512)	$ (41)
U.S. government and agency securities
Debt Securities, Available-for-sale [Line Items]
Debt securities, amortized cost	74		74		266
Debt securities, unrealized gains	0		0		3
Debt securities, unrealized losses	0		0		0
Debt securities, fair value	74		74		269
Foreign government bonds
Debt Securities, Available-for-sale [Line Items]
Debt securities, amortized cost	2		2		0
Debt securities, unrealized gains	0		0		0
Debt securities, unrealized losses	0		0		0
Debt securities, fair value	2		2		0
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Debt securities, amortized cost	0		0		668
Debt securities, unrealized gains	0		0		0
Debt securities, unrealized losses	0		0		0
Debt securities, fair value	0		0		668
Corporate notes and bonds
Debt Securities, Available-for-sale [Line Items]
Debt securities, amortized cost	0		0		608
Debt securities, unrealized gains	0		0		13
Debt securities, unrealized losses	0		0		0
Debt securities, fair value	0		0		621
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Debt securities, amortized cost	0		0		226
Debt securities, unrealized gains	0		0		1
Debt securities, unrealized losses	0		0		0
Debt securities, fair value	$ 0		$ 0		$ 227

X

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X

- Definition Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563 + Details Name: us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: instant

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- Definition Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563 + Details Name: us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: instant

X

- Definition Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=121558606&loc=SL82898722-210454 + Details Name: us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: instant

X

- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(6)) -URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=121558606&loc=SL82898722-210454 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121553693&loc=d3e26610-111562 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563 + Details Name: us-gaap_AvailableForSaleSecuritiesDebtSecurities Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: instant

X

- Definition Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 45 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=99377092&loc=SL75136599-209740 + Details Name: us-gaap_EquitySecuritiesFvNi Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: instant

X

- Definition Amount of unrealized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(3)(d)) -URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 321 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=120269885&loc=SL75117546-209714 + Details Name: us-gaap_EquitySecuritiesFvNiUnrealizedGainLoss Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: duration

X

- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details Name: us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems Namespace Prefix: us-gaap_ Data Type: xbrli:stringItemType Balance Type: na Period Type: duration

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v3.20.2

Financial Instruments - Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Assets
Investments	$ 76	$ 1,785
Publicly traded equity securities	1,477	838
Derivative assets	239	288
Liabilities
Contingent consideration	829	767	$ 755	$ 788
Derivative liabilities	298	97
Foreign government bonds
Assets
Investments	2	0
Corporate notes and bonds
Assets
Investments	0	621
Commercial paper
Assets
Investments	0	668
Asset-backed securities
Assets
Investments	$ 0	227
Liabilities
Primary weighted average life of collateral	5 years
U.S. government and agency securities
Assets
Investments	$ 74	269
Fair Value, Measurements, Recurring
Assets
Investments	1,372	2,243
Other assets	181	380
Derivative assets	239	288
Total assets	1,792	2,911
Liabilities
Contingent consideration	829	767
Derivative liabilities	298	97
Total liabilities	1,127	864
Fair Value, Measurements, Recurring | Foreign exchange contracts
Assets
Derivative assets	116	169
Liabilities
Derivative liabilities	275	95
Fair Value, Measurements, Recurring | Interest rate swap contracts
Assets
Derivative assets	69	15
Fair Value, Measurements, Recurring | Currency options
Assets
Derivative assets	54	104
Liabilities
Derivative liabilities	1	1
Fair Value, Measurements, Recurring | Interest rate swap contracts
Liabilities
Derivative liabilities	0	1
Fair Value, Measurements, Recurring | Forward Contracts
Liabilities
Derivative liabilities	22	0
Fair Value, Measurements, Recurring | Level 1
Assets
Investments	1,370	518
Other assets	181	380
Derivative assets	0	0
Total assets	1,551	898
Liabilities
Contingent consideration	0	0
Derivative liabilities	0	0
Total liabilities	0	0
Fair Value, Measurements, Recurring | Level 1 | Foreign exchange contracts
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Fair Value, Measurements, Recurring | Level 1 | Interest rate swap contracts
Assets
Derivative assets	0	0
Fair Value, Measurements, Recurring | Level 1 | Currency options
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Fair Value, Measurements, Recurring | Level 1 | Interest rate swap contracts
Liabilities
Derivative liabilities	0	0
Fair Value, Measurements, Recurring | Level 1 | Forward Contracts
Liabilities
Derivative liabilities	0	0
Fair Value, Measurements, Recurring | Level 2
Assets
Investments	2	1,725
Other assets	0	0
Derivative assets	239	288
Total assets	241	2,013
Liabilities
Contingent consideration	0	0
Derivative liabilities	298	97
Total liabilities	298	97
Fair Value, Measurements, Recurring | Level 2 | Foreign exchange contracts
Assets
Derivative assets	116	169
Liabilities
Derivative liabilities	275	95
Fair Value, Measurements, Recurring | Level 2 | Interest rate swap contracts
Assets
Derivative assets	69	15
Fair Value, Measurements, Recurring | Level 2 | Currency options
Assets
Derivative assets	54	104
Liabilities
Derivative liabilities	1	1
Fair Value, Measurements, Recurring | Level 2 | Interest rate swap contracts
Liabilities
Derivative liabilities	0	1
Fair Value, Measurements, Recurring | Level 2 | Forward Contracts
Liabilities
Derivative liabilities	22	0
Fair Value, Measurements, Recurring | Level 3
Assets
Investments	0	0
Other assets	0	0
Derivative assets	0	0
Total assets	0	0
Liabilities
Contingent consideration	829	767
Derivative liabilities	0	0
Total liabilities	829	767
Fair Value, Measurements, Recurring | Level 3 | Foreign exchange contracts
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Fair Value, Measurements, Recurring | Level 3 | Interest rate swap contracts
Assets
Derivative assets	0	0
Fair Value, Measurements, Recurring | Level 3 | Currency options
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Fair Value, Measurements, Recurring | Level 3 | Interest rate swap contracts
Liabilities
Derivative liabilities	0	0
Fair Value, Measurements, Recurring | Level 3 | Forward Contracts
Liabilities
Derivative liabilities	0	0
Fair Value, Measurements, Recurring | Foreign government bonds
Assets
Investments	2	0
Fair Value, Measurements, Recurring | Foreign government bonds | Level 1
Assets
Investments	0	0
Fair Value, Measurements, Recurring | Foreign government bonds | Level 2
Assets
Investments	2	0
Fair Value, Measurements, Recurring | Foreign government bonds | Level 3
Assets
Investments	0	0
Fair Value, Measurements, Recurring | Corporate notes and bonds
Assets
Investments	0	621
Fair Value, Measurements, Recurring | Corporate notes and bonds | Level 1
Assets
Investments	0	0
Fair Value, Measurements, Recurring | Corporate notes and bonds | Level 2
Assets
Investments	0	621
Fair Value, Measurements, Recurring | Corporate notes and bonds | Level 3
Assets
Investments	0	0
Fair Value, Measurements, Recurring | Commercial paper
Assets
Investments	0	668
Fair Value, Measurements, Recurring | Commercial paper | Level 1
Assets
Investments	0	0
Fair Value, Measurements, Recurring | Commercial paper | Level 2
Assets
Investments	0	668
Fair Value, Measurements, Recurring | Commercial paper | Level 3
Assets
Investments	0	0
Fair Value, Measurements, Recurring | Asset-backed securities
Assets
Investments	0	227
Fair Value, Measurements, Recurring | Asset-backed securities | Level 1
Assets
Investments	0	0
Fair Value, Measurements, Recurring | Asset-backed securities | Level 2
Assets
Investments	0	227
Fair Value, Measurements, Recurring | Asset-backed securities | Level 3
Assets
Investments	0	0
Fair Value, Measurements, Recurring | U.S. government and agency securities
Assets
Investments	0	209
Other assets	74	60
Fair Value, Measurements, Recurring | U.S. government and agency securities | Level 1
Assets
Investments	0	0
Other assets	74	60
Fair Value, Measurements, Recurring | U.S. government and agency securities | Level 2
Assets
Investments	0	209
Other assets	0	0
Fair Value, Measurements, Recurring | U.S. government and agency securities | Level 3
Assets
Investments	0	0
Other assets	0	0
Fair Value, Measurements, Recurring | Publicly traded equity securities
Assets
Publicly traded equity securities	1,370	518
Other assets	107	320
Fair Value, Measurements, Recurring | Publicly traded equity securities | Level 1
Assets
Publicly traded equity securities	1,370	518
Other assets	107	320
Fair Value, Measurements, Recurring | Publicly traded equity securities | Level 2
Assets
Publicly traded equity securities	0	0
Other assets	0	0
Fair Value, Measurements, Recurring | Publicly traded equity securities | Level 3
Assets
Publicly traded equity securities	0	0
Other assets	$ 0	$ 0

X

- Definition Investments, Primary Weighted Average Life of Collateral + References No definition available. + Details Name: mrk_InvestmentsPrimaryWeightedAverageLifeofCollateral Namespace Prefix: mrk_ Data Type: xbrli:durationItemType Balance Type: na Period Type: duration

X

- Definition Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details Name: us-gaap_AssetsFairValueDisclosure Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: instant

X

- References No definition available. + Details Name: us-gaap_AssetsFairValueDisclosureAbstract Namespace Prefix: us-gaap_ Data Type: xbrli:stringItemType Balance Type: na Period Type: duration

X

- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(6)) -URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=121558606&loc=SL82898722-210454 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121553693&loc=d3e26610-111562 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563 + Details Name: us-gaap_AvailableForSaleSecuritiesDebtSecurities Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: instant

X

- Definition Amount of liability recognized arising from contingent consideration in a business combination. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=120321790&loc=d3e6927-128479 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 35 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=116859824&loc=d3e6819-128478 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 25 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=6911189&loc=d3e6408-128476 + Details Name: us-gaap_BusinessCombinationContingentConsiderationLiability Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: instant

X

- Definition Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=121572278&loc=d3e13433-108611 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 + Details Name: us-gaap_DerivativeAssets Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: instant

X

- Definition Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=121572278&loc=d3e13433-108611 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 20 -Section 55 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226008-175313 + Details Name: us-gaap_DerivativeLiabilities Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: instant

X

- Definition Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 45 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=99377092&loc=SL75136599-209740 + Details Name: us-gaap_EquitySecuritiesFvNi Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: instant

X

- Definition Fair value of financial and nonfinancial obligations. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details Name: us-gaap_LiabilitiesFairValueDisclosure Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: instant

X

- References No definition available. + Details Name: us-gaap_LiabilitiesFairValueDisclosureAbstract Namespace Prefix: us-gaap_ Data Type: xbrli:stringItemType Balance Type: na Period Type: duration

X

- Definition Amount of noncurrent assets classified as other. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.17) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details Name: us-gaap_OtherAssetsNoncurrent Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: instant

X

- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.4) -URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878 + Details Name: us-gaap_TradingSecurities Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: instant

X

- Details Name: us-gaap_FinancialInstrumentAxis=us-gaap_ForeignGovernmentDebtSecuritiesMember Namespace Prefix: Data Type: na Balance Type: Period Type:

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- Details Name: us-gaap_FinancialInstrumentAxis=us-gaap_CorporateDebtSecuritiesMember Namespace Prefix: Data Type: na Balance Type: Period Type:

X

- Details Name: us-gaap_FinancialInstrumentAxis=us-gaap_CommercialPaperMember Namespace Prefix: Data Type: na Balance Type: Period Type:

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- Details Name: us-gaap_FinancialInstrumentAxis=us-gaap_AssetBackedSecuritiesMember Namespace Prefix: Data Type: na Balance Type: Period Type:

X

- Details Name: us-gaap_FinancialInstrumentAxis=us-gaap_USGovernmentAgenciesDebtSecuritiesMember Namespace Prefix: Data Type: na Balance Type: Period Type:

X

- Details Name: us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember Namespace Prefix: Data Type: na Balance Type: Period Type:

X

- Details Name: us-gaap_DerivativeInstrumentRiskAxis=us-gaap_ForeignExchangeContractMember Namespace Prefix: Data Type: na Balance Type: Period Type:

X

- Details Name: us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateSwapMember Namespace Prefix: Data Type: na Balance Type: Period Type:

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- Details Name: us-gaap_DerivativeInstrumentRiskAxis=us-gaap_ForeignExchangeOptionMember Namespace Prefix: Data Type: na Balance Type: Period Type:

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- Details Name: us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateContractMember Namespace Prefix: Data Type: na Balance Type: Period Type:

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- Details Name: us-gaap_DerivativeInstrumentRiskAxis=us-gaap_ForwardContractsMember Namespace Prefix: Data Type: na Balance Type: Period Type:

X

- Details Name: us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member Namespace Prefix: Data Type: na Balance Type: Period Type:

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- Details Name: us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member Namespace Prefix: Data Type: na Balance Type: Period Type:

X

- Details Name: us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member Namespace Prefix: Data Type: na Balance Type: Period Type:

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- Details Name: us-gaap_FinancialInstrumentAxis=us-gaap_EquitySecuritiesMember Namespace Prefix: Data Type: na Balance Type: Period Type:

v3.20.2

Financial Instruments - Information About Changes in Liabilities for Contingent Consideration (Details) $ in Millions	9 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning balance	$ 767	$ 788
Additions	97	0
Changes in estimated fair value	71	52
Payments	(106)	(85)
Fair value, ending balance	829	755
Current liability			$ 140
Contingent consideration	829	$ 755	829
Sanofi Pasteur
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning balance	625
Fair value, ending balance	637
Contingent consideration	$ 625		$ 637
Contingent consideration, measurement input, discount rate (as percent)			0.115
Measurement Input, Discount Rate | Sanofi Pasteur
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Contingent consideration, measurement input, discount rate (as percent)			0.08

X

- Definition Amount of liabilities incurred by the acquirer as part of consideration transferred in a business combination. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 30 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=116859721&loc=d3e6578-128477 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 25 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6911189&loc=d3e6405-128476 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=120321790&loc=d3e6927-128479 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 30 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=116859721&loc=d3e6613-128477 + Details Name: us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: duration

X

- Definition Amount of increase (decrease) in the value of a contingent consideration liability, including, but not limited to, differences arising upon settlement. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 50 -Paragraph 4 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=120321790&loc=d3e7008-128479 + Details Name: us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1 Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: duration

X

- Definition Amount of liability recognized arising from contingent consideration in a business combination. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=120321790&loc=d3e6927-128479 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 35 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=116859824&loc=d3e6819-128478 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 25 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=6911189&loc=d3e6408-128476 + Details Name: us-gaap_BusinessCombinationContingentConsiderationLiability Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: instant

X

- Definition Amount of liability recognized arising from contingent consideration in a business combination, expected to be settled within one year or the normal operating cycle, if longer. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 25 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=6911189&loc=d3e6408-128476 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 35 -Paragraph 1 -Subparagraph b -URI http://asc.fasb.org/extlink&oid=116859824&loc=d3e6819-128478 + Details Name: us-gaap_BusinessCombinationContingentConsiderationLiabilityCurrent Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: instant

X

- Definition Value of input used to measure contingent consideration liability from business combination. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (bbb)(2) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details Name: us-gaap_BusinessCombinationContingentConsiderationLiabilityMeasurementInput Namespace Prefix: us-gaap_ Data Type: xbrli:decimalItemType Balance Type: na Period Type: instant

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- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details Name: us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward Namespace Prefix: us-gaap_ Data Type: xbrli:stringItemType Balance Type: na Period Type: duration

X

- Definition Amount of settlements of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details Name: us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: duration

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- Details Name: us-gaap_MeasurementInputTypeAxis=us-gaap_MeasurementInputDiscountRateMember Namespace Prefix: Data Type: na Balance Type: Period Type:

v3.20.2

Inventories - Inventories (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Inventory Disclosure [Abstract]
Finished goods	$ 2,038	$ 1,772
Raw materials and work in process	6,073	5,650
Supplies	197	207
Total (approximates current cost)	8,308	7,629
Decrease to LIFO cost	(99)	(171)
Total current and noncurrent inventories	8,209	7,458
Recognized as:
Inventories	6,128	5,978
Other assets	$ 2,081	$ 1,480

X

- Definition Total of current and noncurrent inventories. + References No definition available. + Details Name: mrk_InventoryNetAndInventoryNoncurrent Namespace Prefix: mrk_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: instant

X

- Definition Recognized as. + References No definition available. + Details Name: mrk_RecognizedAsAbstract Namespace Prefix: mrk_ Data Type: xbrli:stringItemType Balance Type: na Period Type: duration

X

- References No definition available. + Details Name: us-gaap_InventoryDisclosureAbstract Namespace Prefix: us-gaap_ Data Type: xbrli:stringItemType Balance Type: na Period Type: duration

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- Definition Amount before valuation and LIFO reserves of completed merchandise or goods expected to be sold within one year or operating cycle, if longer. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.6(a)(1)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details Name: us-gaap_InventoryFinishedGoods Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: instant

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- Definition Gross amount, as of the balance sheet date, of merchandise, goods, commodities, or supplies held for future sale or to be used in manufacturing, servicing or production process. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.6(a)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details Name: us-gaap_InventoryGross Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: instant

X

- Definition Amount by which inventory stated at last-in first-out (LIFO) is less than (in excess of) inventory stated at other inventory cost methods. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.6(c)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details Name: us-gaap_InventoryLIFOReserve Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: instant

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- Definition Amount after valuation and LIFO reserves of inventory expected to be sold, or consumed within one year or operating cycle, if longer. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121566466&loc=d3e6676-107765 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.6(a)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details Name: us-gaap_InventoryNet Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: instant

X

- Definition Inventories not expected to be converted to cash, sold or exchanged within the normal operating cycle. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.6(d)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details Name: us-gaap_InventoryNoncurrent Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: instant

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- Definition The aggregate carrying amount as of the balance sheet date of items held by the entity which are partially completed at the time of measurement and unprocessed items that will go through the production process and become part of the final product. Includes supplies used directly or indirectly in the manufacturing or production process. This element may be used when the reporting entity combines work in process and raw materials into an aggregate amount. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.6(a)(3),(4)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details Name: us-gaap_InventoryWorkInProcessAndRawMaterials Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: instant

X

- Definition Amount before valuation and LIFO reserves of other supplies used within the manufacturing or production process expected to be consumed within one year or operating cycle, if longer. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.6(a)(5)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details Name: us-gaap_OtherInventorySupplies Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: instant

v3.20.2

Inventories - Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Inventory [Line Items]
Inventories classified in Other assets	$ 2,081	$ 1,480
Inventories Not Expected to be Sold Within One Year
Inventory [Line Items]
Inventories classified in Other assets	1,800	1,300
Inventories Produced in Preparation for Product Launches
Inventory [Line Items]
Inventories classified in Other assets	$ 288	$ 168

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- Definition Inventories not expected to be converted to cash, sold or exchanged within the normal operating cycle. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.6(d)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details Name: us-gaap_InventoryNoncurrent Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: instant

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v3.20.2

Other Intangibles (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Finite-Lived Intangible Assets [Line Items]
Intangible asset impairment charges	$ 612	$ 693
Sivextro [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible asset impairment charges	$ 612

X

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- Definition The amount of impairment loss recognized in the period resulting from the write-down of the carrying amount of a finite-lived intangible asset to fair value. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 3 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16373-109275 + Details Name: us-gaap_ImpairmentOfIntangibleAssetsFinitelived Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: duration

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v3.20.2

Long-Term Debt - Narrative (Details)	Jun. 30, 2020 USD ($)
Debt Instrument [Line Items]
Face amount of debt	$ 4,500,000,000
0.75% notes due 2026
Debt Instrument [Line Items]
Face amount of debt	$ 1,000,000,000.0
Stated interest rate (as percent)	0.75%
1.45% notes due 2030
Debt Instrument [Line Items]
Face amount of debt	$ 1,250,000,000
Stated interest rate (as percent)	1.45%
2.35% notes due 2040
Debt Instrument [Line Items]
Face amount of debt	$ 1,000,000,000.0
Stated interest rate (as percent)	2.35%
2.45% notes due 2050
Debt Instrument [Line Items]
Face amount of debt	$ 1,250,000,000
Stated interest rate (as percent)	2.45%

X

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- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details Name: us-gaap_DebtInstrumentInterestRateStatedPercentage Namespace Prefix: us-gaap_ Data Type: num:percentItemType Balance Type: na Period Type: instant

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v3.20.2

Contingencies - Narrative (Details) $ in Millions	1 Months Ended	9 Months Ended
	Mar. 31, 2014 Case	Sep. 30, 2020 USD ($) Case Claim	Dec. 31, 2019 USD ($)
Legal Defense Costs
Loss Contingencies [Line Items]
Legal defense costs reserve | $		$ 255	$ 240
Zetia antitrust litigation [Member]
Loss Contingencies [Line Items]
Loss contingency, pending claims, number (in legal matters) | Claim		35
Patents [Member]
Loss Contingencies [Line Items]
Loss contingency, pending claims, number (in legal matters)		3
Loss Contingency, Claims Settled, Number		5
Fosamax
Loss Contingencies [Line Items]
Loss contingency, pending claims, number (in legal matters)		3,590
Fosamax | Femur Fracture Litigation | Federal
Loss Contingencies [Line Items]
Loss contingency, pending claims, number (in legal matters)		970
Loss contingency, claims dismissed, number (in legal matters)	650
Loss contingency, claims on appeal, number (in legal matters)	515
Fosamax | Femur Fracture Litigation | New Jersey state court
Loss Contingencies [Line Items]
Loss contingency, pending claims, number (in legal matters)		2,340
Fosamax | Femur Fracture Litigation | California state court
Loss Contingencies [Line Items]
Loss contingency, pending claims, number (in legal matters)		275
Fosamax | Femur Fracture Litigation | Other state courts
Loss Contingencies [Line Items]
Loss contingency, pending claims, number (in legal matters)		4
Januvia
Loss Contingencies [Line Items]
Loss contingency, pending claims, number (in legal matters) | Claim		1,465
Januvia | Other state courts
Loss Contingencies [Line Items]
Loss contingency, pending claims, number (in legal matters) | Claim		6
Januvia | Cases Company Agreed To Toll Statute Of Limitations
Loss Contingencies [Line Items]
Loss contingency, pending claims, number (in legal matters) | Claim		50

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- Definition Aggregate carrying amount of the estimated litigation liability for known or estimated probable loss from litigation, which may include attorneys' fees and other litigation costs. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=121557415&loc=d3e14326-108349 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.25) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details Name: us-gaap_LitigationReserve Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: instant

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v3.20.2

Equity - Rollforward Reconciliations (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares, beginning balance (in shares)			3,577,103,522
Equity, beginning balance	$ 27,744	$ 27,737	$ 26,001	$ 26,882
Net income attributable to Merck & Co., Inc.	2,941	1,901	9,161	7,487
Other comprehensive income (loss), net of taxes	10	(28)	(190)	155
Cash dividends declared on common stock	(1,558)	(1,392)	(4,656)	(4,262)
Treasury stock shares purchased		(1,405)	(1,281)	(3,730)
Share-based compensation plans and other	151	127	245	487
Net income (loss) attributable to noncontrolling interests	4	6	12	(73)
Distributions attributable to noncontrolling interests	$ (22)	(21)	$ (22)	(21)
Shares, ending balance (in shares)	3,577,103,522		3,577,103,522
Equity, ending balance	$ 29,270	$ 26,925	$ 29,270	$ 26,925
Cash dividends declared on common stock (in dollars per share)	$ 0.61	$ 0.55	$ 1.83	$ 1.65
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares, beginning balance (in shares)	3,577,000,000	3,577,000,000	3,577,000,000	3,577,000,000
Equity, beginning balance	$ 1,788	$ 1,788	$ 1,788	$ 1,788
Shares, ending balance (in shares)	3,577,000,000	3,577,000,000	3,577,000,000	3,577,000,000
Equity, ending balance	$ 1,788	$ 1,788	$ 1,788	$ 1,788
Other Paid-In Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity, beginning balance	39,373	39,484	39,660	38,808
Treasury stock shares purchased				1,000
Share-based compensation plans and other	116	77	(171)	(247)
Equity, ending balance	39,489	39,561	39,489	39,561
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity, beginning balance	49,724	45,295	46,602	42,579
Net income attributable to Merck & Co., Inc.	2,941	1,901	9,161	7,487
Cash dividends declared on common stock	(1,558)	(1,392)	(4,656)	(4,262)
Equity, ending balance	51,107	45,804	51,107	45,804
Accumulated Other Comprehensive Loss
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity, beginning balance	(6,393)	(5,362)	(6,193)	(5,545)
Other comprehensive income (loss), net of taxes	10	(28)	(190)	155
Equity, ending balance	$ (6,383)	$ (5,390)	$ (6,383)	$ (5,390)
Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares, beginning balance (in shares)	1,048,000,000	1,010,000,000	1,038,000,000	985,000,000
Equity, beginning balance	$ (56,850)	$ (53,570)	$ (55,950)	$ (50,929)
Treasury stock shares purchased (in shares)		17,000,000	16,000,000	54,000,000
Treasury stock shares purchased		$ (1,405)	$ (1,281)	$ (4,730)
Share-based compensation plans and other (in shares)	(1,000,000)	(1,000,000)	(7,000,000)	(13,000,000)
Share-based compensation plans and other	$ 35	$ 50	$ 416	$ 734
Shares, ending balance (in shares)	1,047,000,000	1,026,000,000	1,047,000,000	1,026,000,000
Equity, ending balance	$ (56,815)	$ (54,925)	$ (56,815)	$ (54,925)
Non- controlling Interests
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity, beginning balance	102	102	94	181
Net income (loss) attributable to noncontrolling interests	4	6	12	(73)
Distributions attributable to noncontrolling interests	(22)	(21)	(22)	(21)
Equity, ending balance	$ 84	$ 87	$ 84	$ 87

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v3.20.2

Share-Based Compensation Plans - Expense Allocations (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Share-based Payment Arrangement [Abstract]
Pretax share-based compensation expense	$ 126	$ 101	$ 354	$ 306
Income tax benefit	(17)	(14)	(48)	(42)
Total share-based compensation expense, net of taxes	$ 109	$ 87	$ 306	$ 264

X

- Definition Amount, after tax, of expense for award under share-based payment arrangement. + References No definition available. + Details Name: us-gaap_AllocatedShareBasedCompensationExpenseNetOfTax Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: duration

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- Definition Amount of noncash expense for share-based payment arrangement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585 + Details Name: us-gaap_ShareBasedCompensation Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: duration

v3.20.2

Share-Based Compensation Plans - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	4,000,000	3,000,000
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price	$ 77.67	$ 80.05
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 9.93	$ 10.63
Total pretax unrecognized compensation expense related to nonvested stock options, RSU and PSU awards	$ 800
Weighted average period in years of recognition for nonvested stock options, RSU and PSU awards	2 years 1 month 6 days
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)	7,000,000	5,000,000
Weighted-average fair value per share granted (in dollars per share)	$ 77.83	$ 80.03
Performance Share Units (PSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)	773,000	609,000
Weighted-average fair value per share granted (in dollars per share)	$ 75.22	$ 90.50

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v3.20.2

Share-Based Compensation Plans - Assumptions Used for Options Granted (Details)	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Share-based Payment Arrangement [Abstract]
Expected dividend yield	3.10%	3.20%
Risk-free interest rate	0.40%	2.40%
Expected volatility	22.10%	18.70%
Expected life (years)	5 years 9 months 18 days	5 years 10 months 24 days

X

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- Definition Expected term of award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(i) -URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 14.D.2) -URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809 + Details Name: us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1 Namespace Prefix: us-gaap_ Data Type: xbrli:durationItemType Balance Type: na Period Type: duration

v3.20.2

Pension and Other Postretirement Benefit Plans (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Other Postretirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 13	$ 12	$ 39	$ 36
Interest cost	14	17	43	52
Expected return on plan assets	(19)	(18)	(56)	(54)
Amortization of unrecognized prior service credit	(18)	(20)	(54)	(59)
Net loss amortization	(5)	(3)	(13)	(7)
Termination benefits	0	1	0	1
Curtailments	0	(3)	(1)	(4)
Net periodic benefit cost	(15)	(14)	(42)	(35)
U.S. | Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	96	76	270	221
Interest cost	107	115	323	343
Expected return on plan assets	(193)	(202)	(581)	(613)
Amortization of unrecognized prior service credit	(12)	(12)	(37)	(37)
Net loss amortization	75	43	228	113
Termination benefits	1	3	5	7
Curtailments	1	5	4	6
Settlements	2	0	11	0
Net periodic benefit cost	77	28	223	40
International | Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	77	58	225	178
Interest cost	35	44	103	133
Expected return on plan assets	(104)	(106)	(310)	(320)
Amortization of unrecognized prior service credit	(3)	(3)	(9)	(9)
Net loss amortization	32	16	94	47
Termination benefits	1	0	2	1
Curtailments	0	0	(1)	0
Settlements	0	0	2	0
Net periodic benefit cost	$ 38	$ 9	$ 106	$ 30

X

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X

- Definition Amount of prior service cost (credit) recognized in net periodic benefit cost (credit) of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4179-114921 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(5) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 45 -Paragraph 3A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109237824&loc=SL108413299-114919 Reference 4: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 18 -URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4587-114921 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a)(5) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2709-114920 + Details Name: us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: duration

X

- Definition Amount of cost of providing special or contractual termination benefits payable from defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (q) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details Name: us-gaap_DefinedBenefitPlanCostOfProvidingSpecialOrContractualTerminationBenefitRecognizedDuringPeriod Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: duration

X

- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details Name: us-gaap_DefinedBenefitPlanDisclosureLineItems Namespace Prefix: us-gaap_ Data Type: xbrli:stringItemType Balance Type: na Period Type: duration

X

- Definition Amount of expected return (loss) recognized in net periodic benefit (cost) credit, calculated based on expected long-term rate of return and market-related value of plan assets of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4179-114921 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 18 -URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4587-114921 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(3) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 45 -Paragraph 3A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109237824&loc=SL108413299-114919 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2709-114920 + Details Name: us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: duration

X

- Definition Amount of cost recognized for passage of time related to defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(2) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 45 -Paragraph 3A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109237824&loc=SL108413299-114919 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4179-114921 Reference 4: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 18 -URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4587-114921 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2709-114920 + Details Name: us-gaap_DefinedBenefitPlanInterestCost Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: duration

X

- Definition Amount of net periodic benefit cost (credit) for defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2709-114920 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4179-114921 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 18 -URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4587-114921 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details Name: us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: duration

X

- Definition Amount of gain (loss) recognized in net periodic benefit (cost) credit from event reducing expected years of future service of present employees or eliminating accrual of defined benefits for some or all future services of present employees. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 45 -Paragraph 3A -URI http://asc.fasb.org/extlink&oid=109237824&loc=SL108413299-114919 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(7) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a)(7) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2709-114920 + Details Name: us-gaap_DefinedBenefitPlanRecognizedNetGainLossDueToCurtailments Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: duration

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- Definition Amount of gain (loss) recognized in net periodic benefit (cost) credit from irrevocable action relieving primary responsibility for benefit obligation and eliminating risk related to obligation and assets used to effect settlement. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(7) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 45 -Paragraph 3A -URI http://asc.fasb.org/extlink&oid=109237824&loc=SL108413299-114919 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a)(7) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2709-114920 + Details Name: us-gaap_DefinedBenefitPlanRecognizedNetGainLossDueToSettlements1 Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: duration

X

- Definition Amount of cost for actuarial present value of benefits attributed to service rendered by employee for defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (h)(1) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4179-114921 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2709-114920 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 5: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 18 -URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4587-114921 + Details Name: us-gaap_DefinedBenefitPlanServiceCost Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: duration

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X

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v3.20.2

Pension and Other Postretirement Benefit Plans Pension and Other Postretirement Benefit Plans (Narrative) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2020 USD ($)
International
Defined Benefit Plan Disclosure [Line Items]
Expected future employer contributions, current fiscal year	$ 375
Contributions by employer	123
U.S.
Defined Benefit Plan Disclosure [Line Items]
Expected future employer contributions, current fiscal year	200
Contributions by employer	$ 184

X

- Definition Amount of contribution received by defined benefit plan from employer which increases plan assets. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4179-114921 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(01) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2709-114920 Reference 4: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(ii) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 5: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 18 -URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4587-114921 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(01) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details Name: us-gaap_DefinedBenefitPlanContributionsByEmployer Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: duration

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X

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v3.20.2

Other (Income) Expense, Net (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Component of Other Income / Expense of Nonoperating [Line Items]
Interest income	$ (9)	$ (61)	$ (48)	$ (225)
Interest expense	203	231	624	674
Exchange losses	10	38	89	166
Income from investments in equity securities, net (1)	(360)	(16)	(964)	(50)
Net periodic defined benefit plan (credit) cost other than service cost	(88)	(128)	(259)	(409)
Other, net	(68)	(29)	(72)	206
Other (income) expense, net	$ (312)	$ 35	$ (630)	$ 362

X

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X

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- Definition Amount of the cost of borrowed funds accounted for as interest expense. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6450988&loc=d3e26243-108391 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28555-108399 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 22 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8736-108599 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (210.5-03(11)) -URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227 Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.9) -URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260 + Details Name: us-gaap_InterestExpense Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: duration

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- Definition Amount of income (expense) related to nonoperating activities, classified as other. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.9) -URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227 + Details Name: us-gaap_OtherNonoperatingIncomeExpense Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: duration

v3.20.2

Other (Income) Expense, Net Other (Income) Expense, Net - Narrative (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Component of Other Income / Expense of Nonoperating [Line Items]
Interest paid	$ 605	$ 629
Healthcare Services Segment
Component of Other Income / Expense of Nonoperating [Line Items]
Goodwill, Impairment Loss		$ 162

X

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v3.20.2

Taxes on Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Tax Examination [Line Items]
Effective income tax rate (as percent)	14.10%	18.70%	14.90%	14.50%
Internal Revenue Service (IRS) | Domestic Tax Authority
Income Tax Examination [Line Items]
Tax benefit recognized related to settlement				$ 360
Income taxes paid				$ 107

X

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v3.20.2

Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share [Abstract]
Net income attributable to Merck & Co., Inc.	$ 2,941	$ 1,901	$ 9,161	$ 7,487
Average common shares outstanding	2,529	2,558	2,530	2,572
Common shares issuable (1)	9	14	11	15
Average common shares outstanding assuming dilution	2,538	2,572	2,541	2,587
Basic earnings per common share attributable to Merck & Co., Inc. common shareholders	$ 1.16	$ 0.74	$ 3.62	$ 2.91
Earnings per common share assuming dilution attributable to Merck & Co., Inc. common shareholders	$ 1.16	$ 0.74	$ 3.61	$ 2.89
Common shares issuable under share-based compensation plans excluded from diluted earnings per common share because the effect would have been antidilutive (in shares)	5	3	5	2

X

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- Definition The sum of dilutive potential common shares or units used in the calculation of the diluted per-share or per-unit computation. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257 + Details Name: us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment Namespace Prefix: us-gaap_ Data Type: xbrli:sharesItemType Balance Type: na Period Type: duration

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- Definition The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 45 -Paragraph 16 -URI http://asc.fasb.org/extlink&oid=121326447&loc=d3e1505-109256 + Details Name: us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding Namespace Prefix: us-gaap_ Data Type: xbrli:sharesItemType Balance Type: na Period Type: duration

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- Definition Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 45 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=121326447&loc=d3e1448-109256 + Details Name: us-gaap_WeightedAverageNumberOfSharesOutstandingBasic Namespace Prefix: us-gaap_ Data Type: xbrli:sharesItemType Balance Type: na Period Type: duration

v3.20.2

Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Equity, beginning balance	$ 27,744	$ 27,737	$ 26,001	$ 26,882
Other comprehensive income (loss) before reclassification adjustments, pretax	(143)	106	(362)	364
Tax	77	(72)	79	(65)
Other comprehensive income (loss) before reclassification adjustments, net of taxes	(66)	34	(283)	299
Reclassification adjustments, pretax	94	(75)	121	(176)
Tax	(18)	13	(28)	32
Reclassification adjustments, net of taxes	76	(62)	93	(144)
Other comprehensive income (loss), net of taxes	10	(28)	(190)	155
Equity, ending balance	29,270	26,925	29,270	26,925
Derivatives
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Equity, beginning balance	15	66	31	166
Other comprehensive income (loss) before reclassification adjustments, pretax	(195)	186	(126)	183
Tax	41	(39)	27	(38)
Other comprehensive income (loss) before reclassification adjustments, net of taxes	(154)	147	(99)	145
Reclassification adjustments, pretax	22	(71)	(68)	(195)
Tax	(5)	15	14	41
Reclassification adjustments, net of taxes	17	(56)	(54)	(154)
Other comprehensive income (loss), net of taxes	(137)	91	(153)	(9)
Equity, ending balance	(122)	157	(122)	157
Investments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Equity, beginning balance	0	48	18	(78)
Other comprehensive income (loss) before reclassification adjustments, pretax	0	8	3	139
Tax	0	0	0	0
Other comprehensive income (loss) before reclassification adjustments, net of taxes	0	8	3	139
Reclassification adjustments, pretax	0	(25)	(21)	(30)
Tax	0	0	0	0
Reclassification adjustments, net of taxes	0	(25)	(21)	(30)
Other comprehensive income (loss), net of taxes	0	(17)	(18)	109
Equity, ending balance	0	31	0	31
Employee Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Equity, beginning balance	(4,162)	(3,530)	(4,261)	(3,556)
Other comprehensive income (loss) before reclassification adjustments, pretax	2	(4)	(19)	(5)
Tax	1	0	12	6
Other comprehensive income (loss) before reclassification adjustments, net of taxes	3	(4)	(7)	1
Reclassification adjustments, pretax	72	21	210	49
Tax	(13)	(2)	(42)	(9)
Reclassification adjustments, net of taxes	59	19	168	40
Other comprehensive income (loss), net of taxes	62	15	161	41
Equity, ending balance	(4,100)	(3,515)	(4,100)	(3,515)
Cumulative Translation Adjustment
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Equity, beginning balance	(2,246)	(1,946)	(1,981)	(2,077)
Other comprehensive income (loss) before reclassification adjustments, pretax	50	(84)	(220)	47
Tax	35	(33)	40	(33)
Other comprehensive income (loss) before reclassification adjustments, net of taxes	85	(117)	(180)	14
Reclassification adjustments, pretax	0	0	0	0
Tax	0	0	0	0
Reclassification adjustments, net of taxes	0	0	0	0
Other comprehensive income (loss), net of taxes	85	(117)	(180)	14
Equity, ending balance	(2,161)	(2,063)	(2,161)	(2,063)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Equity, beginning balance	(6,393)	(5,362)	(6,193)	(5,545)
Equity, ending balance	$ (6,383)	$ (5,390)	$ (6,383)	$ (5,390)

X

- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details Name: us-gaap_AOCIAttributableToParentNetOfTaxRollForward Namespace Prefix: us-gaap_ Data Type: xbrli:stringItemType Balance Type: na Period Type: duration

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- Definition Amount before tax and reclassification adjustments of other comprehensive income (loss) attributable to parent. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=121641772&loc=SL7669686-108580 + Details Name: us-gaap_OciBeforeReclassificationsBeforeTaxAttributableToParent Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: duration

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- Definition Amount after tax, before reclassification adjustments, of other comprehensive income (loss), attributable to parent. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 55 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=121640130&loc=d3e1436-108581 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=121641772&loc=SL7669686-108580 + Details Name: us-gaap_OciBeforeReclassificationsNetOfTaxAttributableToParent Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: duration

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- Definition Amount of tax expense (benefit) allocated to other comprehensive income (loss) before reclassification adjustment from accumulated other comprehensive income (loss). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=121641772&loc=d3e640-108580 + Details Name: us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsTax Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: duration

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- Definition Amount after tax of other comprehensive income (loss) attributable to parent entity. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 1B -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121641772&loc=SL7669625-108580 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 1A -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=109239629&loc=SL4573702-111684 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 45 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=108774443&loc=SL4569643-111683 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 1A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121641772&loc=SL7669619-108580 Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 45 -Paragraph 19 -URI http://asc.fasb.org/extlink&oid=108774443&loc=SL4569616-111683 + Details Name: us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: duration

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- Definition Amount before tax of reclassification adjustments of other comprehensive income (loss) attributable to parent. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=121641772&loc=SL7669686-108580 + Details Name: us-gaap_ReclassificationFromAociCurrentPeriodBeforeTaxAttributableToParent Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: duration

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- Definition Amount after tax of reclassification adjustments of other comprehensive income (loss) attributable to parent. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=121641772&loc=SL7669686-108580 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 55 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=121640130&loc=d3e1436-108581 + Details Name: us-gaap_ReclassificationFromAociCurrentPeriodNetOfTaxAttributableToParent Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: duration

X

- Definition Amount of tax expense (benefit) of reclassification adjustment from accumulated other comprehensive income (loss). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=121641772&loc=d3e640-108580 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 17A -URI http://asc.fasb.org/extlink&oid=121641772&loc=SL34724391-108580 + Details Name: us-gaap_ReclassificationFromAociCurrentPeriodTax Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: duration

X

- Definition Amount of stockholders' equity (deficit), net of receivables from officers, directors, owners, and affiliates of the entity, attributable to both the parent and noncontrolling interests. Amount excludes temporary equity. 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v3.20.2

Segment Reporting - Narrative (Details) $ in Billions	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) segment	Sep. 30, 2019 USD ($)
Segment Reporting [Abstract]
Number of operating segments | segment			3
Sales discounts | $	$ 3.4	$ 3.0	$ 9.6	$ 8.6

X

- Definition Sales Discounts + References No definition available. + Details Name: mrk_SalesDiscounts Namespace Prefix: mrk_ Data Type: xbrli:monetaryItemType Balance Type: debit Period Type: duration

X

- Definition Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 18 -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8672-108599 + Details Name: us-gaap_NumberOfOperatingSegments Namespace Prefix: us-gaap_ Data Type: xbrli:integerItemType Balance Type: na Period Type: duration

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- References No definition available. + Details Name: us-gaap_SegmentReportingAbstract Namespace Prefix: us-gaap_ Data Type: xbrli:stringItemType Balance Type: na Period Type: duration

v3.20.2

Segment Reporting - Sales of Company's Products (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Sales	$ 12,551	$ 12,397	$ 35,479	$ 34,972
Operating Segments
Segment Reporting Information [Line Items]
Sales	12,540	12,263	35,212	34,622
Other
Segment Reporting Information [Line Items]
Sales	11	134	267	350
United States
Segment Reporting Information [Line Items]
Sales	5,625	5,573	15,396	15,320
United States | Operating Segments
Segment Reporting Information [Line Items]
Sales	5,616	5,563	15,349	15,301
United States | Other
Segment Reporting Information [Line Items]
Sales	9	10	47	19
International
Segment Reporting Information [Line Items]
Sales	6,926	6,824	20,084	19,652
International | Operating Segments
Segment Reporting Information [Line Items]
Sales	6,924	6,699	19,863	19,322
International | Other
Segment Reporting Information [Line Items]
Sales	2	125	221	330
Total Pharmaceutical segment sales | Operating Segments
Segment Reporting Information [Line Items]
Sales	11,320	11,095	31,654	31,218
Total Pharmaceutical segment sales | Operating Segments | Keytruda
Segment Reporting Information [Line Items]
Sales	3,715	3,070	10,387	7,973
Total Pharmaceutical segment sales | Operating Segments | Alliance revenue - Lynparza (1)
Segment Reporting Information [Line Items]
Sales	196	123	519	313
Total Pharmaceutical segment sales | Operating Segments | Alliance revenue - Lenvima (1)
Segment Reporting Information [Line Items]
Sales	142	109	421	280
Total Pharmaceutical segment sales | Operating Segments | Emend
Segment Reporting Information [Line Items]
Sales	39	98	115	336
Total Pharmaceutical segment sales | Operating Segments | Gardasil/Gardasil 9
Segment Reporting Information [Line Items]
Sales	1,187	1,320	2,941	3,044
Total Pharmaceutical segment sales | Operating Segments | ProQuad/M-M-R II/Varivax
Segment Reporting Information [Line Items]
Sales	576	623	1,390	1,794
Total Pharmaceutical segment sales | Operating Segments | Pneumovax 23
Segment Reporting Information [Line Items]
Sales	375	237	748	592
Total Pharmaceutical segment sales | Operating Segments | RotaTeq
Segment Reporting Information [Line Items]
Sales	210	180	601	564
Total Pharmaceutical segment sales | Operating Segments | Vaqta
Segment Reporting Information [Line Items]
Sales	51	62	139	167
Total Pharmaceutical segment sales | Operating Segments | Bridion
Segment Reporting Information [Line Items]
Sales	320	284	843	817
Total Pharmaceutical segment sales | Operating Segments | Noxafil
Segment Reporting Information [Line Items]
Sales	79	177	247	560
Total Pharmaceutical segment sales | Operating Segments | Prevymis
Segment Reporting Information [Line Items]
Sales	77	45	200	115
Total Pharmaceutical segment sales | Operating Segments | Primaxin
Segment Reporting Information [Line Items]
Sales	74	77	189	207
Total Pharmaceutical segment sales | Operating Segments | Invanz
Segment Reporting Information [Line Items]
Sales	51	57	159	206
Total Pharmaceutical segment sales | Operating Segments | Cancidas
Segment Reporting Information [Line Items]
Sales	50	62	148	191
Total Pharmaceutical segment sales | Operating Segments | Cubicin
Segment Reporting Information [Line Items]
Sales	39	52	116	207
Total Pharmaceutical segment sales | Operating Segments | Zerbaxa
Segment Reporting Information [Line Items]
Sales	43	35	112	88
Total Pharmaceutical segment sales | Operating Segments | Simponi
Segment Reporting Information [Line Items]
Sales	209	203	615	625
Total Pharmaceutical segment sales | Operating Segments | Remicade
Segment Reporting Information [Line Items]
Sales	82	101	242	322
Total Pharmaceutical segment sales | Operating Segments | Belsomra
Segment Reporting Information [Line Items]
Sales	81	80	244	223
Total Pharmaceutical segment sales | Operating Segments | Isentress/Isentress HD
Segment Reporting Information [Line Items]
Sales	205	250	646	752
Total Pharmaceutical segment sales | Operating Segments | Zepatier
Segment Reporting Information [Line Items]
Sales	28	83	122	304
Total Pharmaceutical segment sales | Operating Segments | Zetia
Segment Reporting Information [Line Items]
Sales	103	147	384	443
Total Pharmaceutical segment sales | Operating Segments | Vytorin
Segment Reporting Information [Line Items]
Sales	47	57	139	231
Total Pharmaceutical segment sales | Operating Segments | Atozet
Segment Reporting Information [Line Items]
Sales	111	97	348	283
Total Pharmaceutical segment sales | Operating Segments | Alliance revenue - Adempas (2)
Segment Reporting Information [Line Items]
Sales	83	50	216	144
Total Pharmaceutical segment sales | Operating Segments | Adempas
Segment Reporting Information [Line Items]
Sales	55	57	167	158
Total Pharmaceutical segment sales | Operating Segments | Januvia
Segment Reporting Information [Line Items]
Sales	821	807	2,449	2,539
Total Pharmaceutical segment sales | Operating Segments | Janumet
Segment Reporting Information [Line Items]
Sales	506	503	1,499	1,567
Total Pharmaceutical segment sales | Operating Segments | Implanon/Nexplanon
Segment Reporting Information [Line Items]
Sales	189	199	515	581
Total Pharmaceutical segment sales | Operating Segments | NuvaRing
Segment Reporting Information [Line Items]
Sales	58	241	184	700
Total Pharmaceutical segment sales | Operating Segments | Singulair
Segment Reporting Information [Line Items]
Sales	82	152	338	503
Total Pharmaceutical segment sales | Operating Segments | Cozaar/Hyzaar
Segment Reporting Information [Line Items]
Sales	91	116	292	329
Total Pharmaceutical segment sales | Operating Segments | Arcoxia
Segment Reporting Information [Line Items]
Sales	68	72	204	221
Total Pharmaceutical segment sales | Operating Segments | Nasonex
Segment Reporting Information [Line Items]
Sales	41	58	161	226
Total Pharmaceutical segment sales | Operating Segments | Follistim AQ
Segment Reporting Information [Line Items]
Sales	50	62	136	182
Total Pharmaceutical segment sales | Operating Segments | Other pharmaceutical (3)
Segment Reporting Information [Line Items]
Sales	1,186	1,149	3,478	3,431
Total Pharmaceutical segment sales | United States | Operating Segments
Segment Reporting Information [Line Items]
Sales	5,218	5,180	14,202	14,202
Total Pharmaceutical segment sales | United States | Operating Segments | Keytruda
Segment Reporting Information [Line Items]
Sales	2,157	1,743	6,106	4,525
Total Pharmaceutical segment sales | United States | Operating Segments | Alliance revenue - Lynparza (1)
Segment Reporting Information [Line Items]
Sales	107	71	297	186
Total Pharmaceutical segment sales | United States | Operating Segments | Alliance revenue - Lenvima (1)
Segment Reporting Information [Line Items]
Sales	82	65	270	169
Total Pharmaceutical segment sales | United States | Operating Segments | Emend
Segment Reporting Information [Line Items]
Sales	8	42	18	173
Total Pharmaceutical segment sales | United States | Operating Segments | Gardasil/Gardasil 9
Segment Reporting Information [Line Items]
Sales	579	761	1,209	1,579
Total Pharmaceutical segment sales | United States | Operating Segments | ProQuad/M-M-R II/Varivax
Segment Reporting Information [Line Items]
Sales	437	482	1,033	1,325
Total Pharmaceutical segment sales | United States | Operating Segments | Pneumovax 23
Segment Reporting Information [Line Items]
Sales	276	179	478	428
Total Pharmaceutical segment sales | United States | Operating Segments | RotaTeq
Segment Reporting Information [Line Items]
Sales	114	102	355	360
Total Pharmaceutical segment sales | United States | Operating Segments | Vaqta
Segment Reporting Information [Line Items]
Sales	32	36	79	103
Total Pharmaceutical segment sales | United States | Operating Segments | Bridion
Segment Reporting Information [Line Items]
Sales	162	133	412	381
Total Pharmaceutical segment sales | United States | Operating Segments | Noxafil
Segment Reporting Information [Line Items]
Sales	13	77	27	268
Total Pharmaceutical segment sales | United States | Operating Segments | Prevymis
Segment Reporting Information [Line Items]
Sales	32	22	87	60
Total Pharmaceutical segment sales | United States | Operating Segments | Primaxin
Segment Reporting Information [Line Items]
Sales	1	2	2	2
Total Pharmaceutical segment sales | United States | Operating Segments | Invanz
Segment Reporting Information [Line Items]
Sales	1	(1)	7	30
Total Pharmaceutical segment sales | United States | Operating Segments | Cancidas
Segment Reporting Information [Line Items]
Sales	1	0	2	5
Total Pharmaceutical segment sales | United States | Operating Segments | Cubicin
Segment Reporting Information [Line Items]
Sales	11	14	36	78
Total Pharmaceutical segment sales | United States | Operating Segments | Zerbaxa
Segment Reporting Information [Line Items]
Sales	20	20	57	45
Total Pharmaceutical segment sales | United States | Operating Segments | Simponi
Segment Reporting Information [Line Items]
Sales	0	0	0	0
Total Pharmaceutical segment sales | United States | Operating Segments | Remicade
Segment Reporting Information [Line Items]
Sales	0	0	0	0
Total Pharmaceutical segment sales | United States | Operating Segments | Belsomra
Segment Reporting Information [Line Items]
Sales	18	23	67	68
Total Pharmaceutical segment sales | United States | Operating Segments | Isentress/Isentress HD
Segment Reporting Information [Line Items]
Sales	92	102	243	304
Total Pharmaceutical segment sales | United States | Operating Segments | Zepatier
Segment Reporting Information [Line Items]
Sales	6	24	38	96
Total Pharmaceutical segment sales | United States | Operating Segments | Zetia
Segment Reporting Information [Line Items]
Sales	(1)	5	(4)	11
Total Pharmaceutical segment sales | United States | Operating Segments | Vytorin
Segment Reporting Information [Line Items]
Sales	3	5	9	11
Total Pharmaceutical segment sales | United States | Operating Segments | Atozet
Segment Reporting Information [Line Items]
Sales	0	0	0	0
Total Pharmaceutical segment sales | United States | Operating Segments | Alliance revenue - Adempas (2)
Segment Reporting Information [Line Items]
Sales	78	48	200	137
Total Pharmaceutical segment sales | United States | Operating Segments | Adempas
Segment Reporting Information [Line Items]
Sales	0	0	0	0
Total Pharmaceutical segment sales | United States | Operating Segments | Januvia
Segment Reporting Information [Line Items]
Sales	342	367	1,110	1,223
Total Pharmaceutical segment sales | United States | Operating Segments | Janumet
Segment Reporting Information [Line Items]
Sales	105	129	361	462
Total Pharmaceutical segment sales | United States | Operating Segments | Implanon/Nexplanon
Segment Reporting Information [Line Items]
Sales	137	136	374	421
Total Pharmaceutical segment sales | United States | Operating Segments | NuvaRing
Segment Reporting Information [Line Items]
Sales	24	202	85	593
Total Pharmaceutical segment sales | United States | Operating Segments | Singulair
Segment Reporting Information [Line Items]
Sales	4	11	14	24
Total Pharmaceutical segment sales | United States | Operating Segments | Cozaar/Hyzaar
Segment Reporting Information [Line Items]
Sales	5	6	17	16
Total Pharmaceutical segment sales | United States | Operating Segments | Arcoxia
Segment Reporting Information [Line Items]
Sales	0	0	0	0
Total Pharmaceutical segment sales | United States | Operating Segments | Nasonex
Segment Reporting Information [Line Items]
Sales	0	4	9	2
Total Pharmaceutical segment sales | United States | Operating Segments | Follistim AQ
Segment Reporting Information [Line Items]
Sales	20	27	60	80
Total Pharmaceutical segment sales | United States | Operating Segments | Other pharmaceutical (3)
Segment Reporting Information [Line Items]
Sales	352	343	1,144	1,037
Total Pharmaceutical segment sales | International | Operating Segments
Segment Reporting Information [Line Items]
Sales	6,102	5,914	17,452	17,016
Total Pharmaceutical segment sales | International | Operating Segments | Keytruda
Segment Reporting Information [Line Items]
Sales	1,559	1,327	4,281	3,448
Total Pharmaceutical segment sales | International | Operating Segments | Alliance revenue - Lynparza (1)
Segment Reporting Information [Line Items]
Sales	89	53	223	126
Total Pharmaceutical segment sales | International | Operating Segments | Alliance revenue - Lenvima (1)
Segment Reporting Information [Line Items]
Sales	60	44	152	112
Total Pharmaceutical segment sales | International | Operating Segments | Emend
Segment Reporting Information [Line Items]
Sales	31	56	96	163
Total Pharmaceutical segment sales | International | Operating Segments | Gardasil/Gardasil 9
Segment Reporting Information [Line Items]
Sales	608	558	1,732	1,464
Total Pharmaceutical segment sales | International | Operating Segments | ProQuad/M-M-R II/Varivax
Segment Reporting Information [Line Items]
Sales	139	141	356	469
Total Pharmaceutical segment sales | International | Operating Segments | Pneumovax 23
Segment Reporting Information [Line Items]
Sales	99	58	270	164
Total Pharmaceutical segment sales | International | Operating Segments | RotaTeq
Segment Reporting Information [Line Items]
Sales	96	78	246	203
Total Pharmaceutical segment sales | International | Operating Segments | Vaqta
Segment Reporting Information [Line Items]
Sales	19	26	60	65
Total Pharmaceutical segment sales | International | Operating Segments | Bridion
Segment Reporting Information [Line Items]
Sales	157	151	431	437
Total Pharmaceutical segment sales | International | Operating Segments | Noxafil
Segment Reporting Information [Line Items]
Sales	66	100	220	291
Total Pharmaceutical segment sales | International | Operating Segments | Prevymis
Segment Reporting Information [Line Items]
Sales	46	23	113	55
Total Pharmaceutical segment sales | International | Operating Segments | Primaxin
Segment Reporting Information [Line Items]
Sales	73	75	187	204
Total Pharmaceutical segment sales | International | Operating Segments | Invanz
Segment Reporting Information [Line Items]
Sales	50	58	152	176
Total Pharmaceutical segment sales | International | Operating Segments | Cancidas
Segment Reporting Information [Line Items]
Sales	49	62	147	187
Total Pharmaceutical segment sales | International | Operating Segments | Cubicin
Segment Reporting Information [Line Items]
Sales	28	38	80	129
Total Pharmaceutical segment sales | International | Operating Segments | Zerbaxa
Segment Reporting Information [Line Items]
Sales	23	15	54	43
Total Pharmaceutical segment sales | International | Operating Segments | Simponi
Segment Reporting Information [Line Items]
Sales	209	203	615	625
Total Pharmaceutical segment sales | International | Operating Segments | Remicade
Segment Reporting Information [Line Items]
Sales	82	101	242	322
Total Pharmaceutical segment sales | International | Operating Segments | Belsomra
Segment Reporting Information [Line Items]
Sales	63	57	177	155
Total Pharmaceutical segment sales | International | Operating Segments | Isentress/Isentress HD
Segment Reporting Information [Line Items]
Sales	113	149	403	449
Total Pharmaceutical segment sales | International | Operating Segments | Zepatier
Segment Reporting Information [Line Items]
Sales	22	59	83	208
Total Pharmaceutical segment sales | International | Operating Segments | Zetia
Segment Reporting Information [Line Items]
Sales	103	142	389	432
Total Pharmaceutical segment sales | International | Operating Segments | Vytorin
Segment Reporting Information [Line Items]
Sales	44	52	130	219
Total Pharmaceutical segment sales | International | Operating Segments | Atozet
Segment Reporting Information [Line Items]
Sales	111	97	348	283
Total Pharmaceutical segment sales | International | Operating Segments | Alliance revenue - Adempas (2)
Segment Reporting Information [Line Items]
Sales	5	2	16	7
Total Pharmaceutical segment sales | International | Operating Segments | Adempas
Segment Reporting Information [Line Items]
Sales	55	57	167	158
Total Pharmaceutical segment sales | International | Operating Segments | Januvia
Segment Reporting Information [Line Items]
Sales	479	440	1,339	1,317
Total Pharmaceutical segment sales | International | Operating Segments | Janumet
Segment Reporting Information [Line Items]
Sales	400	375	1,138	1,105
Total Pharmaceutical segment sales | International | Operating Segments | Implanon/Nexplanon
Segment Reporting Information [Line Items]
Sales	52	62	142	160
Total Pharmaceutical segment sales | International | Operating Segments | NuvaRing
Segment Reporting Information [Line Items]
Sales	34	39	98	107
Total Pharmaceutical segment sales | International | Operating Segments | Singulair
Segment Reporting Information [Line Items]
Sales	78	140	324	479
Total Pharmaceutical segment sales | International | Operating Segments | Cozaar/Hyzaar
Segment Reporting Information [Line Items]
Sales	86	110	275	313
Total Pharmaceutical segment sales | International | Operating Segments | Arcoxia
Segment Reporting Information [Line Items]
Sales	68	72	204	221
Total Pharmaceutical segment sales | International | Operating Segments | Nasonex
Segment Reporting Information [Line Items]
Sales	41	55	152	224
Total Pharmaceutical segment sales | International | Operating Segments | Follistim AQ
Segment Reporting Information [Line Items]
Sales	31	35	76	102
Total Pharmaceutical segment sales | International | Operating Segments | Other pharmaceutical (3)
Segment Reporting Information [Line Items]
Sales	834	804	2,334	2,394
Total Animal Health segment sales | Operating Segments
Segment Reporting Information [Line Items]
Sales	1,220	1,122	3,535	3,271
Total Animal Health segment sales | Operating Segments | Livestock
Segment Reporting Information [Line Items]
Sales	758	726	2,145	2,007
Total Animal Health segment sales | Operating Segments | Companion Animals
Segment Reporting Information [Line Items]
Sales	462	396	1,390	1,264
Total Animal Health segment sales | United States | Operating Segments
Segment Reporting Information [Line Items]
Sales	398	337	1,124	966
Total Animal Health segment sales | United States | Operating Segments | Livestock
Segment Reporting Information [Line Items]
Sales	164	144	448	406
Total Animal Health segment sales | United States | Operating Segments | Companion Animals
Segment Reporting Information [Line Items]
Sales	234	193	676	560
Total Animal Health segment sales | International | Operating Segments
Segment Reporting Information [Line Items]
Sales	822	785	2,411	2,305
Total Animal Health segment sales | International | Operating Segments | Livestock
Segment Reporting Information [Line Items]
Sales	594	582	1,697	1,601
Total Animal Health segment sales | International | Operating Segments | Companion Animals
Segment Reporting Information [Line Items]
Sales	228	203	714	704
Other segment sales (4) | Operating Segments
Segment Reporting Information [Line Items]
Sales	0	46	23	133
Other segment sales (4) | United States | Operating Segments
Segment Reporting Information [Line Items]
Sales	0	46	23	133
Other segment sales (4) | International | Operating Segments
Segment Reporting Information [Line Items]
Sales	$ 0	$ 0	$ 0	$ 1

X

- Definition Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 22 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8736-108599 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 28 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=75031198&loc=d3e14064-108612 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 32 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 32 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8933-108599 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 22 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8736-108599 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 40 -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9031-108599 Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 30 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8906-108599 Reference 9: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 41 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9038-108599 Reference 10: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 42 -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9054-108599 Reference 11: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08(g)(1)(ii)) -URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690 Reference 12: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 235 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-05(b)(2)) -URI http://asc.fasb.org/extlink&oid=120399901&loc=d3e537907-122884 Reference 13: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03(1)) -URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227 + Details Name: us-gaap_Revenues Namespace Prefix: us-gaap_ Data Type: xbrli:monetaryItemType Balance Type: credit Period Type: duration

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details Name: us-gaap_SegmentReportingInformationLineItems Namespace Prefix: us-gaap_ Data Type: xbrli:stringItemType Balance Type: na Period Type: duration

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- Details Name: srt_ProductOrServiceAxis=mrk_RotateqMember Namespace Prefix: Data Type: na Balance Type: Period Type:

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v3.20.2

Segment Reporting - Revenues by Geographic Area (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue from External Customer [Line Items]
Sales	$ 12,551	$ 12,397	$ 35,479	$ 34,972
United States
Revenue from External Customer [Line Items]
Sales	5,625	5,573	15,396	15,320
Europe, Middle East and Africa
Revenue from External Customer [Line Items]
Sales	3,454	3,189	10,059	9,452
China
Revenue from External Customer [Line Items]
Sales	1,016	914	2,715	2,423
Japan
Revenue from External Customer [Line Items]
Sales	828	919	2,506	2,639
Asia Pacific (other than China and Japan)
Revenue from External Customer [Line Items]
Sales	735	756	2,129	2,217
Latin America
Revenue from External Customer [Line Items]
Sales	604	671	1,670	1,889
Other
Revenue from External Customer [Line Items]
Sales	$ 289	$ 375	$ 1,004	$ 1,032

X

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v3.20.2

Segment Reporting - Profits to Income Before Taxes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Profits	$ 3,428	$ 2,347	$ 10,784	$ 8,673
Interest income	9	61	48	225
Interest expense	(203)	(231)	(624)	(674)
Depreciation and amortization			(2,721)	(2,716)
Research and development	(3,390)	(3,204)	(7,721)	(7,324)
Restructuring costs	(114)	(232)	(269)	(444)
Total segment profits
Segment Reporting Information [Line Items]
Profits	8,424	8,168	23,347	22,678
Total segment profits | Pharmaceutical segment
Segment Reporting Information [Line Items]
Profits	7,974	7,747	22,010	21,437
Total segment profits | Animal Health segment
Segment Reporting Information [Line Items]
Profits	451	423	1,336	1,243
Total segment profits | Other segment
Segment Reporting Information [Line Items]
Profits	(1)	(2)	1	(2)
Other profits
Segment Reporting Information [Line Items]
Profits	(12)	101	188	226
Unallocated
Segment Reporting Information [Line Items]
Interest income	9	61	48	225
Interest expense	(203)	(231)	(624)	(674)
Depreciation and amortization	(395)	(382)	(1,173)	(1,169)
Research and development	(3,272)	(3,110)	(7,364)	(7,045)
Amortization of purchase accounting adjustments	(285)	(329)	(879)	(1,105)
Restructuring costs	(114)	(232)	(269)	(444)
Other unallocated, net	$ (724)	$ (1,699)	$ (2,490)	$ (4,019)

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