Equity Investments	12 Months Ended
Dec. 31, 2019
Equity Method Investments And Joint Ventures [Abstract]
Equity Investments	10. Equity Investments The carrying value of our equity investments in domestic and foreign companies was $793.2 million at December 31, 2019 ($869.9 million at December 31, 2018), and is recorded in other assets in the consolidated balance sheets. NUMIT Nucor owns a 50% economic and voting interest in NuMit LLC (“NuMit”). NuMit owns 100% of the equity interest in Steel Technologies LLC, an operator of 26 sheet processing facilities located throughout the United States, Canada and Mexico. Nucor accounts for the investment in NuMit (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 NuMit was $319.8 million at December 31, 2019 ($337.2 million at December 31, 2018). Nucor received distributions of $36.5 million, $29.2 million and $48.3 million from NuMit during 2019, 2018 and 2017, 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 $263.0 million at December 31, 2019 ($269.1 million at December 31, 2018). Nucor’s 50% share of the total net assets of Duferdofin Nucor was $115.8 million at December 31, 2019, resulting in a basis difference of $147.2 million due to 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) and finite-lived intangible assets. This basis difference, excluding the portion attributable to goodwill, is being amortized based on the remaining estimated useful lives of the various underlying net assets, as appropriate. Amortization expense associated with the fair value step-up was $8.9 million, $9.3 million and $8.9 million in 2019, 2018 and 2017, respectively. As of December 31, 2019, Nucor had outstanding notes receivable of €35.0 million ($39.3 million) from Duferdofin Nucor (€35.0 million, or $40.2 million, as of December 31, 2018). 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 was extended to January 31, 2022 during the first quarter of 2018. As of December 31, 2019 and 2018, the notes receivable were classified in other assets in the consolidated balance sheets. 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 ($179.5 million) at December 31, 2019. As of December 31, 2019, there was €147.0 million ($164.9 million) outstanding under that facility (€155.0 million, or $178.0 million, as of December 31, 2018). 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-JFE plant construction is substantially complete and operations are expected to begin in the first half of 2020. 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 $163.2 million at December 31, 2019 ($135.7 million at December 31, 2018). 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, 2020. Under the Facility, the maximum amount Nucor-JFE could borrow was $65.0 million as of December 31, 2019. The Facility is uncommitted. As of December 31, 2019, there was no outstanding balance under the Facility. 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 at 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 last assessed its equity investment in Duferdofin Nucor for impairment during the fourth quarter of 2019 due to the protracted challenging steel market conditions in Europe. After completing its assessment, the Company determined that the estimated fair value exceeded its carrying amount by a sufficient amount and that there was no need to record an impairment charge. The assumptions that most significantly affect the fair value determination include projected cash flows and the discount rate. It is reasonably possible that material deviation of future performance from the estimates used in our most recent valuation could result in impairment of our investment in Duferdofin Nucor. We will continue to monitor for potential triggering events that could affect the carrying value of our investment in Duferdofin Nucor as a result of future market conditions and any changes in our business strategy.

Equity Investments

12 Months Ended

Dec. 31, 2019

Equity Method Investments And Joint Ventures [Abstract]

10. Equity Investments

The carrying value of our equity investments in domestic and foreign companies was $793.2 million at December 31, 2019 ($869.9 million at December 31, 2018), and is recorded in other assets in the consolidated balance sheets.

NUMIT

Nucor owns a 50% economic and voting interest in NuMit LLC (“NuMit”). NuMit owns 100% of the equity interest in Steel Technologies LLC, an operator of 26 sheet processing facilities located throughout the United States, Canada and Mexico. Nucor accounts for the investment in NuMit (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 NuMit was $319.8 million at December 31, 2019 ($337.2 million at December 31, 2018). Nucor received distributions of $36.5 million, $29.2 million and $48.3 million from NuMit during 2019, 2018 and 2017, 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 $263.0 million at December 31, 2019 ($269.1 million at December 31, 2018). Nucor’s 50% share of the total net assets of Duferdofin Nucor was $115.8 million at December 31, 2019, resulting in a basis difference of $147.2 million due to 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) and finite-lived intangible assets. This basis difference, excluding the portion attributable to goodwill, is being amortized based on the remaining estimated useful lives of the various underlying net assets, as appropriate. Amortization expense associated with the fair value step-up was $8.9 million, $9.3 million and $8.9 million in 2019, 2018 and 2017, respectively.

As of December 31, 2019, Nucor had outstanding notes receivable of €35.0 million ($39.3 million) from Duferdofin Nucor (€35.0 million, or $40.2 million, as of December 31, 2018). 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 was extended to January 31, 2022 during the first quarter of 2018. As of December 31, 2019 and 2018, the notes receivable were classified in other assets in the consolidated balance sheets.

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 ($179.5 million) at December 31, 2019. As of December 31, 2019, there was €147.0 million ($164.9 million) outstanding under that facility (€155.0 million, or $178.0 million, as of December 31, 2018). 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-JFE plant construction is substantially complete and operations are expected to begin in the first half of 2020. 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 $163.2 million at December 31, 2019 ($135.7 million at December 31, 2018).

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, 2020. Under the Facility, the maximum amount Nucor-JFE could borrow was $65.0 million as of December 31, 2019. The Facility is uncommitted. As of December 31, 2019, there was no outstanding balance under the Facility. 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 at 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 last assessed its equity investment in Duferdofin Nucor for impairment during the fourth quarter of 2019 due to the protracted challenging steel market conditions in Europe. After completing its assessment, the Company determined that the estimated fair value exceeded its carrying amount by a sufficient amount and that there was no need to record an impairment charge. The assumptions that most significantly affect the fair value determination include projected cash flows and the discount rate. It is reasonably possible that material deviation of future performance from the estimates used in our most recent valuation could result in impairment of our investment in Duferdofin Nucor. We will continue to monitor for potential triggering events that could affect the carrying value of our investment in Duferdofin Nucor as a result of future market conditions and any changes in our business strategy.