Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 29, 2012	Oct. 01, 2011	Sep. 29, 2012	Oct. 01, 2011	Dec. 31, 2011
Segment Reporting Information [Line Items]
Net sales to external customers	$ 4,801,206	$ 5,252,144	$ 14,977,999	$ 15,193,887
Earnings (loss) before income taxes and noncontrolling interests	191,775	284,215	633,030	1,027,757
Segment assets	14,997,247		14,997,247		14,570,350
Steel Mills [Member]
Segment Reporting Information [Line Items]
Net sales to external customers	3,204,898	3,617,867	10,307,698	10,635,850
Intercompany sales	669,326	599,005	1,985,535	1,815,673
Earnings (loss) before income taxes and noncontrolling interests	217,430	427,723	943,818	1,476,323
Segment assets	7,688,875		7,688,875		6,440,868
Steel Products [Member]
Segment Reporting Information [Line Items]
Net sales to external customers	1,006,366	958,224	2,840,055	2,565,728
Intercompany sales	17,179	14,444	52,958	38,691
Earnings (loss) before income taxes and noncontrolling interests	(10,252)	(10,527)	(34,094)	(56,432)
Segment assets	3,020,164		3,020,164		2,903,281
Raw Materials [Member]
Segment Reporting Information [Line Items]
Net sales to external customers	475,322	535,948	1,455,134	1,618,956
Intercompany sales	2,080,150	2,572,705	7,441,529	8,047,832
Earnings (loss) before income taxes and noncontrolling interests	14,535	26,263	44,223	140,352
Segment assets	3,191,854		3,191,854		2,925,651
All Other [Member]
Segment Reporting Information [Line Items]
Net sales to external customers	114,620	140,105	375,112	373,353
Intercompany sales	1,550	4,742	12,344	21,093
Earnings (loss) before income taxes and noncontrolling interests	937	737	780	5,014
Segment assets	203,429		203,429		152,107
Corporate/Eliminations [Member]
Segment Reporting Information [Line Items]
Intercompany sales	(2,768,205)	(3,190,896)	(9,492,366)	(9,923,289)
Earnings (loss) before income taxes and noncontrolling interests	(30,875)	(159,981)	(321,697)	(537,500)
Segment assets	$ 892,925		$ 892,925		$ 2,148,443