Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015 segment	Mar. 31, 2014	Dec. 31, 2014
Segment Information
Number of reporting segments	3us-gaap_NumberOfReportableSegments
Segment Reporting Information
Total net sales	$ 2,047,435us-gaap_SalesRevenueNet	$ 1,830,082us-gaap_SalesRevenueNet
Operating income (loss)	99,771us-gaap_OperatingIncomeLoss	80,932us-gaap_OperatingIncomeLoss
Income (loss) before income taxes	40,492	50,994
Depreciation and amortization	72,822	57,568
Capital expenditures	33,351	24,841
Assets	6,735,838us-gaap_Assets	5,913,857us-gaap_Assets	7,311,027us-gaap_Assets
Liabilities	3,812,745us-gaap_Liabilities	3,279,527us-gaap_Liabilities
U.S.
Segment Reporting Information
Total net sales	1,923,975	1,715,518
Non-U.S.
Segment Reporting Information
Total net sales	123,460	114,564
Steel Operations
Segment Reporting Information
Capital expenditures	14,686	18,606
Metals Recycling/Ferrous Resources
Segment Reporting Information
Capital expenditures	17,658	5,779
Steel Fabrication Operations
Segment Reporting Information
Capital expenditures	1,037	311
Other.
Segment Reporting Information
Capital expenditures	(30)	145
Operating Segment
Segment Reporting Information
Total net sales	2,047,435	1,830,082
Operating Segment \| Steel Operations
Segment Reporting Information
Total net sales	1,434,322	1,161,330
Operating income (loss)	111,540	105,643
Income (loss) before income taxes	85,906	91,998
Depreciation and amortization	48,614	27,377
Assets	4,130,841	2,731,246
Liabilities	617,868	576,643
Operating Segment \| Steel Operations \| Other segments
Segment Reporting Information
Total net sales	48,903	43,732
Operating Segment \| Steel Operations \| U.S.
Segment Reporting Information
Total net sales	1,313,426	1,061,079
Operating Segment \| Steel Operations \| Non-U.S.
Segment Reporting Information
Total net sales	71,993	56,519
Operating Segment \| Metals Recycling/Ferrous Resources
Segment Reporting Information
Total net sales	705,792	919,702
Operating income (loss)	(17,066)	(15,519)
Income (loss) before income taxes	(24,670)	(22,696)
Depreciation and amortization	20,838	26,621
Assets	2,022,821	2,537,892
Liabilities	521,404	613,611
Operating Segment \| Metals Recycling/Ferrous Resources \| Other segments
Segment Reporting Information
Total net sales	227,078	343,928
Operating Segment \| Metals Recycling/Ferrous Resources \| U.S.
Segment Reporting Information
Total net sales	427,411	517,957
Operating Segment \| Metals Recycling/Ferrous Resources \| Non-U.S.
Segment Reporting Information
Total net sales	51,303	57,817
Operating Segment \| Steel Fabrication Operations
Segment Reporting Information
Total net sales	161,028	115,861
Operating income (loss)	21,361	3,126
Income (loss) before income taxes	19,594	1,652
Depreciation and amortization	2,230	2,222
Assets	289,814	263,688
Liabilities	46,328	17,022
Operating Segment \| Steel Fabrication Operations \| Other segments
Segment Reporting Information
Total net sales	4
Operating Segment \| Steel Fabrication Operations \| U.S.
Segment Reporting Information
Total net sales	161,024	115,861
Operating Segment \| Other.
Segment Reporting Information
Total net sales	28,967	27,522
Operating income (loss)	(19,920)	(16,545)
Income (loss) before income taxes	(44,194)	(24,187)
Depreciation and amortization	1,190	1,399
Assets	481,726	609,206
Liabilities	2,810,613	2,290,332
Operating Segment \| Other. \| Other segments
Segment Reporting Information
Total net sales	6,689	6,673
Operating Segment \| Other. \| U.S.
Segment Reporting Information
Total net sales	22,114	20,621
Operating Segment \| Other. \| Non-U.S.
Segment Reporting Information
Total net sales	164	228
Eliminations
Segment Reporting Information
Total net sales	(282,674)	(394,333)
Operating income (loss)	3,856	4,227
Income (loss) before income taxes	3,856	4,227
Depreciation and amortization	(50)	(51)
Assets	(189,364)	(228,175)
Liabilities	(183,468)	(218,081)
Eliminations \| Other segments
Segment Reporting Information
Total net sales	$ (282,674)	$ (394,333)

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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