of loss are shared equally between the members. Nucor’s investment in NuMit was $316.7 million at July 4, 2020 ($319.8 million at December 31, 2019). Nucor received distributions of $2.0 million and $27.4 million from NuMit during the first six months of 2020 and 2019, respectively.

Duferdofin Nucor

Nucor owns a 50% economic and voting interest in Duferdofin Nucor S.r.l. (“Duferdofin Nucor”), an Italian steel manufacturer, and accounts for the investment (on a one-month lag basis) under the equity method, as control and risk of loss are shared equally between the members.

Nucor’s investment in Duferdofin Nucor was $2.5 million at July 4, 2020 ($263.0 million at December 31, 2019). Nucor’s 50% share of the total net assets of Duferdofin Nucor was $115.9 million at July 4, 2020, resulting in a negative basis difference of $113.4 million. This is due to the $255.0 million impairment charge taken against the Company’s investment in Duferdofin Nucor in the first half of 2020 as discussed below, offset by the step-up to fair value of certain assets and liabilities attributable to Duferdofin Nucor, as well as the identification of goodwill ($86.5 million at December 31, 2019) and finite-lived intangible assets. This basis difference prior to the impairment charge, excluding the portion attributable to goodwill, was being amortized based on the remaining estimated useful lives of the various underlying net assets, as appropriate, through the first quarter of 2020. Beginning with the second quarter of 2020, the negative basis difference of $113.4 million began amortizing based on the remaining useful lives of the various underlying net assets, as appropriate. Amortization expense associated with the negative basis in the second quarter of 2020 was income of $1.8 million, compared to an expense of $2.3 million in the second quarter of 2019, associated with the fair value step-up. Net amortization expense was $0.3 million and $4.5 million in the first six months of 2020 and 2019, respectively.     

As of July 4, 2020, Nucor had outstanding notes receivable of €35.0 million ($39.4 million) from Duferdofin Nucor (€35.0 million, or $39.3 million, as of December 31, 2019). The notes receivable bear interest at a rate that resets annually on September 30 to the 12-month Euro Interbank Offered Rate plus 0.75% per year. The maturity date of the principal amounts is January 31, 2022. As of July 4, 2020 and December 31, 2019, the notes receivable were classified in other assets in the condensed consolidated balance sheets. These notes were fully reserved in connection with the $255.0 million impairment charge taken against the Company’s investment in Duferdofin Nucor in the first half of 2020 as discussed below.

Nucor has issued a guarantee for its ownership percentage (50%) of Duferdofin Nucor’s borrowings under Facility A of a Structured Trade Finance Facilities Agreement (“Facility A”). The fair value of the guarantee is immaterial. In April 2018, Duferdofin Nucor amended and extended Facility A to mature on April 16, 2021. The maximum amount Duferdofin Nucor could borrow under Facility A was €160.0 million ($180.0 million) at July 4, 2020. As of July 4, 2020, there was €147.0 million ($165.4 million) outstanding under that facility (€147.0 million, or $164.9 million, as of December 31, 2019). If Duferdofin Nucor fails to pay when due any amounts for which it is obligated under Facility A, Nucor could be required to pay 50% of such amounts pursuant to and in accordance with the terms of its guarantee. Any indebtedness of Duferdofin Nucor to Nucor is effectively subordinated to the indebtedness of Duferdofin Nucor under Facility A. Nucor has not recorded any liability associated with this guarantee.

Nucor-JFE

Nucor owns a 50% economic and voting interest in Nucor-JFE Steel Mexico, S. de R.L. de C.V. (“Nucor-JFE”), a 50-50 joint venture with JFE Steel Corporation of Japan, to build and operate a galvanized sheet steel plant in central Mexico. Nucor accounts for the investment in Nucor-JFE (on a one-month lag basis) under the equity method, as control and risk of loss are shared equally between the members. Nucor’s investment in Nucor-JFE was $153.6 million at July 4, 2020 ($163.2 million at December 31, 2019).

On January 16, 2019, Nucor entered into an agreement to guarantee a percentage, equal to its ownership percentage (50%), of Nucor-JFE’s borrowings under the General Financing Agreement and Promissory Note (the “Facility”). The fair value of the guarantee is immaterial. Nucor’s guarantee expires on April 30, 2021. Under the Facility, the maximum amount Nucor-JFE could borrow was $65.0 million as of July 4, 2020. The Facility is uncommitted. As of July 4, 2020, there was $35.0 million outstanding under the Facility (none as of December 31, 2019). If Nucor-JFE fails to pay when due any amounts for which it is obligated under the Facility, Nucor could be required to pay 50% of such amounts pursuant to and in accordance with the terms of its guarantee. Nucor has not recorded any liability associated with this guarantee.

Nucor-JFE has other credit facilities that Nucor has agreed to guarantee. The principal amount subject to guarantee by Nucor for these other credit facilities was $25.0 million as of July 4, 2020 ($25.0 million as of December 31, 2019). The fair value of the guarantees is immaterial. If Nucor-JFE fails to pay when due any amounts for which it is obligated, Nucor could be required to pay such amounts pursuant to and in accordance with the terms of its guarantee. Nucor has not recorded any liability associated with these guarantees.

All Equity Investments

Nucor reviews its equity investments for impairment if and when circumstances indicate that a decline in fair value below their carrying amounts may have occurred. Nucor determined that a triggering event occurred in the first quarter of 2020 with respect to its equity method investment in Duferdofin Nucor due to adverse developments in the joint venture’s commercial outlook, which have been exacerbated by the COVID-19 pandemic, all of which have negatively impacted the joint venture’s strategic direction. After completing its impairment assessment, Nucor determined that the carrying amount exceeded its estimated fair value and the impairment condition was considered to be other than temporary. Therefore, Nucor recorded a $250.0 million impairment charge in the first quarter of 2020 and a $5.0 million impairment charge in the second quarter of 2020 against its investment in Duferdofin Nucor. Any additional capital contributions, if necessary, that Nucor makes to Duferdofin Nucor will be subject to impairment. Additionally, the Company fully reserved its €35.0 million ($39.4 million) outstanding note receivable from Duferdofin Nucor due to an assessment of the likelihood of collection in light of these adverse developments and its effective subordination to Facility A. These charges are included in losses on assets in the condensed consolidated statements of earnings. The assumptions that most significantly affect the fair value determination include projected cash flows and the discount rate. The Company-specific inputs for measuring fair value are considered “Level 3” or unobservable inputs that are not corroborated by market data under applicable fair value authoritative guidance, as quoted market prices are not available.

It is reasonably possible that material deviation of future performance from the estimates used in our most recent valuation could result in further impairment of our investment in Duferdofin Nucor and affect any potential liability associated with the Company’s guarantee of the indebtedness of Duferdofin Nucor as discussed above.

measurements for Nucor’s derivatives are classified under Level 2 because such measurements are based on published market prices for similar assets or are estimated based on observable inputs such as interest rates, yield curves, credit risks, spot and future commodity prices, and spot and future exchange rates.

The fair value of short-term and long-term debt, including current maturities, was approximately $6.00 billion at July 4, 2020 ($4.81 billion at December 31, 2019). The debt fair value estimates are classified under Level 2 because such estimates are based on readily available market prices of our debt at July 4, 2020 and December 31, 2019, or similar debt with the same maturities, ratings and interest rates.

Disclosures are required for certain assets and liabilities that are measured at fair value, but are recognized and disclosed on a nonrecurring basis in periods subsequent to initial recognition. For Nucor, our equity investment in Duferdofin Nucor was measured at fair value as a result of the impairment charges recorded in the first six months of 2020 (see Note 5).

Stock options granted to employees who are eligible for retirement on the date of the grant are expensed immediately since these awards vest upon retirement from the Company. Retirement, for purposes of vesting in these stock options, means termination of employment after satisfying age and years of service requirements. Similarly, stock options granted to employees who will become retirement-eligible prior to the end of the vesting term are expensed over the period through which the employee will become retirement-eligible. Compensation expense for stock options granted to employees who will not become retirement-eligible prior to the end of the vesting term is recognized on a straight-line basis over the vesting period. Compensation expense for stock options was $1.8 million and $3.8 million in the second quarter of 2020 and 2019, respectively, and $2.1 million and $4.1 million in the first six months of 2020 and 2019, respectively. As of July 4, 2020, unrecognized compensation expense related to stock options was $3.1 million, which is expected to be recognized over a weighted-average period of 2.6 years.

Restricted Stock Units

Nucor annually grants restricted stock units (“RSUs”) to key employees, officers and non-employee directors. The RSUs granted to key employees and officers vest and are converted to common stock in three equal installments on each of the first three anniversaries of the grant date provided that a portion of the RSUs awarded to an officer prior to 2018 vest only upon the officer’s retirement. Retirement, for purposes of vesting in these RSUs only, means termination of employment with approval of the Compensation and Executive Development Committee of the Board of Directors after satisfying age and years of service requirements. RSUs granted to a non-employee director are fully vested on the grant date and are payable to the non-employee director in the form of common stock after the termination of the director’s service on the Board of Directors.

RSUs granted to employees who are eligible for retirement on the date of the grant are expensed immediately, and RSUs granted to employees who will become retirement-eligible prior to the end of the vesting term are expensed over the period through which the employee will become retirement-eligible since these awards vest upon retirement from the Company. Compensation expense for RSUs granted to employees who will not become retirement-eligible prior to the end of the vesting term is recognized on a straight-line basis over the vesting period.

Cash dividend equivalents are paid to holders of RSUs each quarter. Dividend equivalents paid on RSUs expected to vest are recognized as a reduction in retained earnings.

The fair value of an RSU is determined based on the closing price of Nucor’s common stock on the date of the grant.

Compensation expense for RSUs was $26.8 million and $41.3 million in the second quarter of 2020 and 2019, respectively, and $36.8 million and $48.1 million in the first six months of 2020 and 2019, respectively. As of July 4, 2020, unrecognized compensation expense related to unvested RSUs was $75.1 million, which is expected to be recognized over a weighted-average period of 1.7 years.

Restricted Stock Awards

Prior to their expiration effective December 31, 2017, the Nucor Corporation Senior Officers Long-Term Incentive Plan and the Nucor Corporation Senior Officers Annual Incentive Plan authorized the award of shares of common stock to

officers subject to certain conditions and restrictions. Effective January 1, 2018, the Company adopted supplements to the Omnibus Plan with terms that permit the award of shares of common stock to officers subject to the conditions and restrictions described below, which are substantially similar to those of the expired Senior Officers Long-Term Incentive Plan and Senior Officers Annual Incentive Plan. The expired Senior Officers Long-Term Incentive Plan, together with the applicable supplement, is referred to below as the “LTIP,” and the expired Senior Officers Annual Incentive Plan, together with the applicable supplement, is referred to below as the “AIP.”

The LTIP provides for the award of shares of restricted common stock at the end of each LTIP performance measurement period at no cost to officers if certain financial performance goals are met during the period. One-third of the LTIP restricted stock award vests upon each of the first three anniversaries of the award date or, if earlier, upon the officer’s attainment of age 55 while employed by Nucor. Although participants are entitled to cash dividends and may vote such awarded shares, the sale or transfer of such shares is limited during the restricted period.

The AIP provides for the payment of annual cash incentive awards. An AIP participant may elect, however, to defer payment of up to one-half of an AIP award. In such event, the deferred AIP award is converted into common stock units and credited with a deferral incentive, in the form of additional common stock units, equal to 25% of the number of common stock units attributable to the deferred AIP award. Common stock units attributable to deferred AIP awards are fully vested. Common stock units credited as a deferral incentive vest upon the AIP participant’s attainment of age 55 while employed by Nucor. Vested common stock units are paid to AIP participants in the form of shares of common stock following their termination of employment with Nucor.

Compensation expense for common stock and common stock units awarded under the AIP and the LTIP is recorded over the performance measurement and vesting periods based on the anticipated number and market value of shares of common stock and common stock units to be awarded. Compensation expense for anticipated awards based upon Nucor’s financial performance, exclusive of amounts payable in cash, was $2.8 million and $3.7 million in the second quarter of 2020 and 2019, respectively, and $2.5 million and $9.1 million in the first six months of 2020 and 2019, respectively. As of July 4, 2020, unrecognized compensation expense related to unvested restricted stock awards was $2.0 million, which is expected to be recognized over a weighted-average period of 1.8 years.