Segments - Segments (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 03, 2015	Oct. 04, 2014	Oct. 03, 2015	Oct. 04, 2014	Dec. 31, 2014
Segment Reporting Information [Line Items]
Net sales	$ 4,225,514	$ 5,701,869	$ 12,982,563	$ 16,101,388
Earnings (loss) before income taxes and noncontrolling interests	354,271	403,985	689,538	853,351
Total assets	15,269,468		15,269,468		$ 15,615,927
Steel Mills [Member]
Segment Reporting Information [Line Items]
Earnings (loss) before income taxes and noncontrolling interests	260,776	502,703	676,404	1,188,638
Total assets	7,851,349		7,851,349		8,528,623
Steel Products [Member]
Segment Reporting Information [Line Items]
Earnings (loss) before income taxes and noncontrolling interests	96,167	63,890	199,261	108,222
Total assets	2,638,770		2,638,770		2,731,320
Raw Materials [Member]
Segment Reporting Information [Line Items]
Earnings (loss) before income taxes and noncontrolling interests	(43,177)	(19,321)	(122,778)	(20,597)
Total assets	3,492,948		3,492,948		3,858,254
Net Sales to External Customers [Member]
Segment Reporting Information [Line Items]
Net sales	4,225,514	5,701,869	12,982,563	16,101,388
Net Sales to External Customers [Member] | Steel Mills [Member]
Segment Reporting Information [Line Items]
Net sales	2,816,441	3,898,031	8,838,424	11,179,935
Net Sales to External Customers [Member] | Steel Products [Member]
Segment Reporting Information [Line Items]
Net sales	1,081,047	1,142,043	3,018,077	3,052,135
Net Sales to External Customers [Member] | Raw Materials [Member]
Segment Reporting Information [Line Items]
Net sales	328,026	661,795	1,126,062	1,869,318
Intercompany Eliminations [Member] | Steel Mills [Member]
Segment Reporting Information [Line Items]
Net sales	551,300	797,396	1,703,554	2,248,462
Intercompany Eliminations [Member] | Steel Products [Member]
Segment Reporting Information [Line Items]
Net sales	26,271	34,215	66,788	82,257
Intercompany Eliminations [Member] | Raw Materials [Member]
Segment Reporting Information [Line Items]
Net sales	1,689,458	2,492,453	5,210,317	7,463,951
Intercompany Eliminations [Member] | Corporate/Eliminations [Member]
Segment Reporting Information [Line Items]
Net sales	(2,267,029)	(3,324,064)	(6,980,659)	(9,794,670)
Earnings (loss) before income taxes and noncontrolling interests	40,505	$ (143,287)	(63,349)	$ (422,912)
Total assets	$ 1,286,401		$ 1,286,401		$ 497,730