Segments - Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Apr. 04, 2015	Apr. 05, 2014	Dec. 31, 2014
Segment Reporting Information [Line Items]
Net sales	$ 4,399,440	$ 5,108,444
Earnings (loss) before income taxes and noncontrolling interests	119,045	207,501
Total assets	14,855,438		15,615,927
Steel Mills [Member]
Segment Reporting Information [Line Items]
Earnings (loss) before income taxes and noncontrolling interests	217,128	317,797
Total assets	8,008,557		8,535,910
Steel Products [Member]
Segment Reporting Information [Line Items]
Earnings (loss) before income taxes and noncontrolling interests	32,458	1,720
Total assets	2,629,853		2,711,798
Raw Materials [Member]
Segment Reporting Information [Line Items]
Earnings (loss) before income taxes and noncontrolling interests	(41,497)	8,359
Total assets	3,741,180		3,927,159
Net Sales to External Customers [Member]
Segment Reporting Information [Line Items]
Net sales	4,399,440	5,108,444
Net Sales to External Customers [Member] | Steel Mills [Member]
Segment Reporting Information [Line Items]
Net sales	3,053,339	3,607,764
Net Sales to External Customers [Member] | Steel Products [Member]
Segment Reporting Information [Line Items]
Net sales	921,384	874,169
Net Sales to External Customers [Member] | Raw Materials [Member]
Segment Reporting Information [Line Items]
Net sales	424,717	626,511
Intercompany Eliminations [Member] | Steel Mills [Member]
Segment Reporting Information [Line Items]
Net sales	574,983	708,866
Intercompany Eliminations [Member] | Steel Products [Member]
Segment Reporting Information [Line Items]
Net sales	19,497	21,500
Intercompany Eliminations [Member] | Raw Materials [Member]
Segment Reporting Information [Line Items]
Net sales	1,832,918	2,528,006
Intercompany Eliminations [Member] | Corporate/Eliminations [Member]
Segment Reporting Information [Line Items]
Net sales	(2,427,398)	(3,258,372)
Earnings (loss) before income taxes and noncontrolling interests	(89,044)	(120,375)
Total assets	$ 475,848		$ 441,060