Equity Investments - Additional Information (Detail)	3 Months Ended			1 Months Ended			3 Months Ended							3 Months Ended		3 Months Ended
	Mar. 30, 2013 USD ($)	Mar. 31, 2012 USD ($)	Dec. 31, 2012 USD ($)	Nov. 30, 2012 Hunter Ridge Energy Services LLC [Member]	Mar. 30, 2013 Hunter Ridge Energy Services LLC [Member] USD ($)	Dec. 31, 2012 Hunter Ridge Energy Services LLC [Member] USD ($)	Mar. 30, 2013 Duferdofin Nucor S.R.L. [Member] USD ($)	Mar. 31, 2012 Duferdofin Nucor S.R.L. [Member] USD ($)	Mar. 30, 2013 Duferdofin Nucor S.R.L. [Member] EUR (€)	Dec. 31, 2012 Duferdofin Nucor S.R.L. [Member] USD ($)	Dec. 31, 2012 Duferdofin Nucor S.R.L. [Member] EUR (€)	Mar. 30, 2013 Duferdofin Nucor S.R.L. [Member] EURO [Member] EUR (€)	Dec. 31, 2012 Duferdofin Nucor S.R.L. [Member] EURO [Member] EUR (€)	Mar. 30, 2013 NuMit [Member] USD ($)	Dec. 31, 2012 NuMit [Member] USD ($)	Mar. 30, 2013 Steel Technologies LLC [Member] USD ($)
Schedule of Equity Method Investments [Line Items]
Equity method investment	$ 855,200,000		$ 855,900,000		$ 114,500,000	$ 95,400,000	$ 433,300,000			$ 454,100,000				$ 289,300,000	$ 288,400,000
Period used for lag basis, in months				1 month			1 month							1 month
Equity method investment, ownership percentage				50.00%			50.00%							50.00%		100.00%
Equity method investments, share of net assets							46,200,000
Step-up to fair value of certain assets and liabilities							387,100,000
Step-up to fair value of equity method investment, portion related to identification of goodwill							309,500,000
Amortization expense and other purchase accounting adjustments due to fair value step-up	19,048,000	16,584,000					2,900,000	2,800,000
Due from related parties, noncurrent							44,900,000		35,000,000		35,000,000
Notes receivable, related parties, interest rate							1.69%									1.21%
Interest rate per year in excess of Euribor as of date of the notes	1.00%
Equity method investment's credit facilities with parent company, maturity date							Jan. 31, 2016							Oct. 21, 2014
Equity method investment's credit facilities, amount												112,500,000
Total amount outstanding under equity method investment's credit facilities							129,500,000			134,800,000		101,000,000	102,000,000
Line of credit facility, maturity period							Oct. 26, 2013									Apr. 01, 2013
Guarantor obligation percentage of exposure in case of default							50.00%
Number of sheet processing facilities operated by Steel Technologies														23
Investment in joint venture														221,300,000
Notes receivable, related parties																40,000,000
Basis points in excess of LIBOR on note receivable from related party																0.90%
Line of credit extended to joint venture, amount outstanding																39,500,000
Line of credit extended to joint venture																130,000,000
Line of credit facility extended to joint venture, interest rate																1.81%
Amended line of credit extended to joint venture																$ 100,000,000