Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012 segment	Dec. 31, 2011	Dec. 31, 2010
Segment Information
Number of reporting segments									3
Segment Reporting Information
Net Sales, External									$ 6,851,365	$ 7,519,048	$ 5,948,184
Net Sales, External Non-U.S.									438,869	478,452	352,703
Total net sales	1,705,001	1,693,390	1,909,803	1,982,040	1,858,345	2,043,455	2,079,731	2,015,969	7,290,234	7,997,500	6,300,887
Operating income (loss)	94,929	72,721	103,699	119,816	82,490	108,785	188,219	205,326	391,165	584,820	364,753
Income (loss) before income taxes									204,066	424,319	213,459
Depreciation and amortization									225,216	222,607	224,698
Capital expenditures									223,525	167,007	133,394
Assets	5,815,416				5,979,226				5,815,416	5,979,226	5,589,934
Liabilities	3,338,760				3,608,632				3,338,760	3,608,632	3,458,804
Steel Operations
Segment Reporting Information
Net Sales, External									4,294,437	4,676,898	3,726,869
Net Sales, External Non-U.S.									212,351	182,319	103,061
Net Sales, Other segments									194,320	211,089	169,709
Total net sales									4,701,108	5,070,306	3,999,639
Operating income (loss)									495,640	658,120	439,795
Income (loss) before income taxes									425,509	574,108	363,352
Depreciation and amortization									104,222	108,477	112,471
Capital expenditures									55,786	43,998	51,695
Assets	2,485,235				2,598,767				2,485,235	2,598,767	2,551,885
Liabilities	525,351				495,425				525,351	495,425	422,764
Metals Recycling and Ferrous Resources Operations
Segment Reporting Information
Net Sales, External									2,116,537	2,473,511	1,966,518
Net Sales, External Non-U.S.									226,061	295,552	248,870
Net Sales, Other segments									1,269,198	1,383,505	963,644
Total net sales									3,611,796	4,152,568	3,179,032
Operating income (loss)									(36,508)	26,597	19,686
Income (loss) before income taxes									(70,433)	(16,706)	(26,988)
Depreciation and amortization									103,993	101,893	102,027
Capital expenditures									159,768	103,142	55,982
Assets	2,568,233				2,561,722				2,568,233	2,561,722	2,464,835
Liabilities	484,017				528,629				484,017	528,629	444,170
Steel Fabrication Operations
Segment Reporting Information
Net Sales, External									371,084	275,783	177,055
Net Sales, Other segments									322	625	323
Total net sales									371,406	276,408	177,378
Operating income (loss)									2,114	(6,584)	(25,056)
Income (loss) before income taxes									(4,580)	(13,573)	(30,539)
Depreciation and amortization									8,025	6,751	5,894
Capital expenditures									5,735	2,205	492
Assets	242,747				227,663				242,747	227,663	206,810
Liabilities	15,983				13,768				15,983	13,768	18,361
Other
Segment Reporting Information
Net Sales, External									69,307	92,856	77,742
Net Sales, External Non-U.S.									457	581	772
Net Sales, Other segments									17,698	11,711	9,841
Total net sales									87,462	105,148	88,355
Operating income (loss)									(66,829)	(95,141)	(66,189)
Income (loss) before income taxes									(143,178)	(121,233)	(88,007)
Depreciation and amortization									9,180	5,690	4,493
Capital expenditures									2,236	17,662	28,857
Assets	714,069				789,322				714,069	789,322	562,961
Liabilities	2,497,750				2,759,894				2,497,750	2,759,894	2,746,798
Eliminations
Segment Reporting Information
Net Sales, Other segments									(1,481,538)	(1,606,930)	(1,143,517)
Total net sales									(1,481,538)	(1,606,930)	(1,143,517)
Operating income (loss)									(3,252)	1,828	(3,483)
Income (loss) before income taxes									(3,252)	1,723	(4,359)
Depreciation and amortization									(204)	(204)	(187)
Capital expenditures											(3,632)
Assets	(194,868)				(198,248)				(194,868)	(198,248)	(196,557)
Liabilities	$ (184,341)				$ (189,084)				$ (184,341)	$ (189,084)	$ (173,289)