Segments - Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Oct. 04, 2014	Sep. 28, 2013	Oct. 04, 2014	Sep. 28, 2013	Dec. 31, 2013
Segment Reporting Information [Line Items]
Net sales	$ 5,701,869	$ 4,940,936	$ 16,101,388	$ 14,157,296
Earnings before income taxes and noncontrolling interests	403,985	248,202	853,351	553,862
Segment assets	15,493,594		15,493,594		15,203,283
Steel Mills [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes and noncontrolling interests	502,703	310,591	1,188,638	819,951
Segment assets	8,489,079		8,489,079		8,365,023
Steel Products [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes and noncontrolling interests	63,890	31,018	108,222	51,167
Segment assets	3,028,321		3,028,321		2,861,403
Raw Materials [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes and noncontrolling interests	(19,321)	(493)	(20,597)	13,261
Segment assets	4,026,534		4,026,534		3,956,913
Net Sales To External Customers [Member]
Segment Reporting Information [Line Items]
Net sales	5,701,869	4,940,936	16,101,388	14,157,296
Net Sales To External Customers [Member] | Steel Mills [Member]
Segment Reporting Information [Line Items]
Net sales	3,898,031	3,435,884	11,179,935	9,901,471
Net Sales To External Customers [Member] | Steel Products [Member]
Segment Reporting Information [Line Items]
Net sales	1,142,043	964,153	3,052,135	2,690,604
Net Sales To External Customers [Member] | Raw Materials [Member]
Segment Reporting Information [Line Items]
Net sales	661,795	540,899	1,869,318	1,565,221
Intercompany Eliminations [Member]
Segment Reporting Information [Line Items]
Net sales	0	0	0	0
Intercompany Eliminations [Member] | Steel Mills [Member]
Segment Reporting Information [Line Items]
Net sales	797,396	652,077	2,248,462	1,924,222
Intercompany Eliminations [Member] | Steel Products [Member]
Segment Reporting Information [Line Items]
Net sales	34,215	24,909	82,257	75,036
Intercompany Eliminations [Member] | Raw Materials [Member]
Segment Reporting Information [Line Items]
Net sales	2,492,453	2,391,502	7,463,951	6,738,485
Intercompany Eliminations [Member] | Corporate/Eliminations [Member]
Segment Reporting Information [Line Items]
Net sales	(3,324,064)	(3,068,488)	(9,794,670)	(8,737,743)
Earnings before income taxes and noncontrolling interests	(143,287)	(92,914)	(422,912)	(330,517)
Segment assets	$ (50,340)		$ (50,340)		$ 19,944