Segment Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) segment	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Segment Reporting Information
Number of reporting segments | segment			3
Total net sales	$ 1,950,923	$ 2,339,016	$ 6,003,365	$ 6,238,859
Operating income (loss)	131,029	188,643	308,359	401,480
Income (loss) before income taxes	93,706	134,667	175,806	289,270
Depreciation and amortization	74,211	65,957	221,306	181,966
Capital expenditures	30,286	24,531	86,458	82,906
Assets	6,842,541	7,578,283	6,842,541	7,578,283	$ 7,311,027
Liabilities	3,886,756	4,540,294	3,886,756	4,540,294
U.S.
Segment Reporting Information
Total net sales	1,831,665	2,224,545	5,643,000	5,900,728
Non-U.S.
Segment Reporting Information
Total net sales	119,258	114,471	360,365	338,131
Operating Segment
Segment Reporting Information
Total net sales	1,950,923	2,339,016	6,003,365	6,238,859
Operating Segment | Steel Operations
Segment Reporting Information
Total net sales	1,407,533	1,526,532	4,271,091	4,022,768
Operating income (loss)	124,712	202,600	338,690	469,204
Income (loss) before income taxes	102,566	187,072	269,187	426,676
Depreciation and amortization	52,404	35,265	154,616	96,010
Capital expenditures	21,975	12,506	52,324	48,209
Assets	4,096,188	4,663,142	4,096,188	4,663,142
Liabilities	676,097	830,172	676,097	830,172
Operating Segment | Steel Operations | Other segments
Segment Reporting Information
Total net sales	56,146	75,321	158,609	188,854
Operating Segment | Steel Operations | U.S.
Segment Reporting Information
Total net sales	1,285,459	1,400,370	3,902,162	3,675,696
Operating Segment | Steel Operations | Non-U.S.
Segment Reporting Information
Total net sales	65,928	50,841	210,320	158,218
Operating Segment | Metals Recycling Operations
Segment Reporting Information
Total net sales	616,460	953,483	1,913,921	2,725,728
Operating income (loss)	(3,555)	8,489	229	27,362
Income (loss) before income taxes	(6,967)	3,863	(12,780)	12,394
Depreciation and amortization	15,913	18,769	50,207	56,898
Capital expenditures	6,286	7,769	17,332	16,242
Assets	1,588,821	1,842,485	1,588,821	1,842,485
Liabilities	309,191	401,111	309,191	401,111
Operating Segment | Metals Recycling Operations | Other segments
Segment Reporting Information
Total net sales	270,888	355,835	751,542	1,024,447
Operating Segment | Metals Recycling Operations | U.S.
Segment Reporting Information
Total net sales	294,357	534,348	1,014,753	1,522,334
Operating Segment | Metals Recycling Operations | Non-U.S.
Segment Reporting Information
Total net sales	51,215	63,300	147,626	178,947
Operating Segment | Steel Fabrication Operations
Segment Reporting Information
Total net sales	174,956	190,036	490,509	440,749
Operating income (loss)	36,733	19,474	85,754	30,190
Income (loss) before income taxes	35,108	17,877	80,581	25,628
Depreciation and amortization	2,300	2,974	6,688	7,597
Capital expenditures	935	477	2,506	1,324
Assets	372,673	315,381	372,673	315,381
Liabilities	84,379	34,386	84,379	34,386
Operating Segment | Steel Fabrication Operations | Other segments
Segment Reporting Information
Total net sales	2	43	18	43
Operating Segment | Steel Fabrication Operations | U.S.
Segment Reporting Information
Total net sales	173,047	189,993	488,584	440,706
Operating Segment | Steel Fabrication Operations | Non-U.S.
Segment Reporting Information
Total net sales	1,907		1,907
Operating Segment | Other
Segment Reporting Information
Total net sales	83,219	136,708	267,127	333,756
Operating income (loss)	(28,401)	(42,960)	(117,273)	(129,260)
Income (loss) before income taxes	(38,541)	(75,185)	(162,141)	(179,412)
Depreciation and amortization	3,645	9,000	9,948	21,615
Capital expenditures	1,090	3,779	14,296	17,131
Assets	898,772	929,041	898,772	929,041
Liabilities	2,923,253	3,436,135	2,923,253	3,436,135
Operating Segment | Other | Other segments
Segment Reporting Information
Total net sales	4,209	36,544	29,114	70,798
Operating Segment | Other | U.S.
Segment Reporting Information
Total net sales	78,802	99,834	237,501	261,992
Operating Segment | Other | Non-U.S.
Segment Reporting Information
Total net sales	208	330	512	966
Eliminations
Segment Reporting Information
Total net sales	(331,245)	(467,743)	(939,283)	(1,284,142)
Operating income (loss)	1,540	1,040	959	3,984
Income (loss) before income taxes	1,540	1,040	959	3,984
Depreciation and amortization	(51)	(51)	(153)	(154)
Assets	(113,913)	(171,766)	(113,913)	(171,766)
Liabilities	(106,164)	(161,510)	(106,164)	(161,510)
Eliminations | Other segments
Segment Reporting Information
Total net sales	$ (331,245)	$ (467,743)	$ (939,283)	$ (1,284,142)