Segment Information - Results (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Segment Reporting Information
Total net sales	$ 1,741,301	$ 2,047,435
Operating income (loss)	131,965	99,771
Income (loss) before income taxes	96,714	40,492
Depreciation and amortization	73,985	72,822
Capital expenditures	27,708	33,351
Assets	6,391,642		$ 6,202,082
U.S.
Segment Reporting Information
Total net sales	1,648,393	1,923,974
Non-U.S.
Segment Reporting Information
Total net sales	92,908	123,461
Operating Segment
Segment Reporting Information
Total net sales	1,741,301	2,047,435
Operating Segment | Steel Operations
Segment Reporting Information
Total net sales	1,258,388	1,434,322
Operating income (loss)	132,275	114,965
Income (loss) before income taxes	109,375	89,331
Depreciation and amortization	52,483	50,970
Capital expenditures	23,904	16,200
Assets	3,836,481
Operating Segment | Steel Operations | Other segments
Segment Reporting Information
Total net sales	41,212	48,903
Operating Segment | Steel Operations | U.S.
Segment Reporting Information
Total net sales	1,156,969	1,313,426
Operating Segment | Steel Operations | Non-U.S.
Segment Reporting Information
Total net sales	60,207	71,993
Operating Segment | Metals Recycling Operations
Segment Reporting Information
Total net sales	487,185	652,011
Operating income (loss)	2,767	(4,498)
Income (loss) before income taxes	(223)	(10,536)
Depreciation and amortization	14,580	17,280
Capital expenditures	3,080	6,415
Assets	1,048,643
Operating Segment | Metals Recycling Operations | Other segments
Segment Reporting Information
Total net sales	217,778	226,416
Operating Segment | Metals Recycling Operations | U.S.
Segment Reporting Information
Total net sales	236,757	374,292
Operating Segment | Metals Recycling Operations | Non-U.S.
Segment Reporting Information
Total net sales	32,650	51,303
Operating Segment | Steel Fabrication Operations
Segment Reporting Information
Total net sales	180,081	161,028
Operating income (loss)	32,016	21,361
Income (loss) before income taxes	30,016	19,594
Depreciation and amortization	2,821	2,230
Capital expenditures	604	1,037
Assets	315,659
Operating Segment | Steel Fabrication Operations | Other segments
Segment Reporting Information
Total net sales	26	4
Operating Segment | Steel Fabrication Operations | U.S.
Segment Reporting Information
Total net sales	180,041	161,024
Operating Segment | Steel Fabrication Operations | Non-U.S.
Segment Reporting Information
Total net sales	14
Operating Segment | Other
Segment Reporting Information
Total net sales	75,889	93,600
Operating income (loss)	(31,930)	(35,902)
Income (loss) before income taxes	(39,291)	(61,742)
Depreciation and amortization	4,152	2,393
Capital expenditures	120	9,699
Assets	1,295,859
Operating Segment | Other | Other segments
Segment Reporting Information
Total net sales	1,226	18,203
Operating Segment | Other | U.S.
Segment Reporting Information
Total net sales	74,626	75,232
Operating Segment | Other | Non-U.S.
Segment Reporting Information
Total net sales	37	165
Eliminations
Segment Reporting Information
Total net sales	(260,242)	(293,526)
Operating income (loss)	(3,163)	3,845
Income (loss) before income taxes	(3,163)	3,845
Depreciation and amortization	(51)	(51)
Assets	(105,000)
Eliminations | Other segments
Segment Reporting Information
Total net sales	$ (260,242)	$ (293,526)