Equity Investments (Detail)	3 Months Ended	9 Months Ended			3 Months Ended		9 Months Ended						9 Months Ended				9 Months Ended
	Oct. 01, 2011 USD ($)	Sep. 29, 2012 USD ($)	Oct. 01, 2011 USD ($)	Dec. 31, 2011 USD ($)	Sep. 29, 2012 Duferdofin Nucor S.R.L. [Member] USD ($)	Oct. 01, 2011 Duferdofin Nucor S.R.L. [Member] USD ($)	Sep. 29, 2012 Duferdofin Nucor S.R.L. [Member] USD ($)	Oct. 01, 2011 Duferdofin Nucor S.R.L. [Member] USD ($)	Sep. 29, 2012 Duferdofin Nucor S.R.L. [Member] EUR (€)	Dec. 31, 2011 Duferdofin Nucor S.R.L. [Member] USD ($)	Dec. 31, 2011 Duferdofin Nucor S.R.L. [Member] EUR (€)	Sep. 29, 2012 Duferdofin Nucor S.R.L. [Member] EURO [Member] EUR (€)	Sep. 29, 2012 Duferdofin Nucor S.R.L. [Member] Minimum [Member]	Sep. 29, 2012 Duferdofin Nucor S.R.L. [Member] Maximum [Member]	Sep. 29, 2012 NuMit [Member] USD ($)	Dec. 31, 2011 NuMit [Member] USD ($)	Sep. 29, 2012 Steel Technologies LLC [Member] USD ($)
Schedule of Equity Method Investments [Line Items]
Equity method investment		$ 746,900,000		$ 775,700,000	$ 441,300,000		$ 441,300,000			$ 493,900,000					$ 280,700,000	$ 259,300,000
Period used for lag basis, in months							1								1
Equity method investment, ownership percentage					50.00%		50.00%								50.00%		100.00%
Equity method investments, share of net assets					47,500,000		47,500,000
Step-up to fair value of certain assets and liabilities					393,800,000		393,800,000
Step-up to fair value of equity method investment, portion related to identification of goodwill							311,700,000
Amortization expense and other purchase accounting adjustments due to fair value step-up		53,518,000	51,675,000		2,700,000	3,000,000	8,300,000	9,100,000
Due from related parties, noncurrent					45,200,000		45,200,000		35,000,000		30,000,000
Notes receivable, related parties, interest rate													2.34%	3.12%			1.36%
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												104,000,000
Number of sheet processing facilities operated by Steel Technologies															24
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															90.00%
Line of credit extended to joint venture, amount outstanding																	70,000,000
Line of credit extended to joint venture																	130,000,000
Line of credit facility extended to joint venture, interest rate																	1.84%
Amended line of credit extended to joint venture																	130,000,000
Line of credit facility, maturity period																	Apr. 01, 2013
Impairment charge against investment in Duferdofin Nucor	$ 13,900,000	$ 30,000,000