Equity Investments - Additional Information (Detail) € in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) Sheet	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2019 EUR (€)	Jan. 16, 2019 USD ($)	Dec. 31, 2018 EUR (€)
Schedule Of Equity Method Investments [Line Items]
Equity method investments	$ 793,200,000	$ 869,900,000
Amortization	85,742,000	88,758,000	$ 91,228,000
NuMit LLC [Member]
Schedule Of Equity Method Investments [Line Items]
Equity method investments	$ 319,800,000	337,200,000
Equity method investment, ownership percentage	50.00%			50.00%
Period used for lag basis, in months	1 month
Distributions from affiliates	$ 36,500,000	29,200,000	48,300,000
Steel Technologies LLC [Member]
Schedule Of Equity Method Investments [Line Items]
Equity method investment, ownership percentage	100.00%			100.00%
Number of sheet processing facilities operated by Steel Technologies | Sheet	26
Duferdofin Nucor S.r.l. [Member]
Schedule Of Equity Method Investments [Line Items]
Equity method investments	$ 263,000,000.0	269,100,000
Equity method investment, ownership percentage	50.00%			50.00%
Period used for lag basis, in months	1 month
Equity method investments, share of net assets	$ 115,800,000
Basis difference due to the step-up to fair value of certain assets and liabilities	147,200,000
Step-up to fair value of equity method investment, portion related to identification of goodwill	86,500,000
Amortization	8,900,000	9,300,000	$ 8,900,000
Due from related parties, noncurrent	$ 39,300,000	40,200,000		€ 35.0		€ 35.0
Interest rate per year in excess of Euribor as of date of the notes	0.75%
Equity method investments notes payable with parent company, maturity date	Jan. 31, 2022
Duferdofin Nucor S.r.l. [Member] | Facility A [Member]
Schedule Of Equity Method Investments [Line Items]
Equity method investments credit facilities subject to guarantee, amount	$ 179,500,000			160.0
Total amount outstanding under equity method investments credit facilities	$ 164,900,000	178,000,000.0		€ 147.0		€ 155.0
Guarantor obligation percentage of exposure in case of default	50.00%			50.00%
Line of credit facility, maturity period	Apr. 16, 2021
Nucor-JFE [Member]
Schedule Of Equity Method Investments [Line Items]
Equity method investments	$ 163,200,000	$ 135,700,000
Equity method investment, ownership percentage	50.00%			50.00%	50.00%
Principal amount subject to guarantee for other credit facilities	$ 25,000,000.0
Nucor-JFE [Member] | General Financing Agreement and Promissory Note [Member]
Schedule Of Equity Method Investments [Line Items]
Equity method investments credit facilities subject to guarantee, amount					$ 65,000,000.0
Total amount outstanding under equity method investments credit facilities	$ 0
Guarantor obligation percentage of exposure in case of default	50.00%			50.00%