CONSOLIDATED STATEMENTS OF OPERATIONS (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Net sales
Unrelated parties	$ 7,718,714	$ 6,060,933	$ 3,810,378
Related parties	278,786	239,954	148,428
Total net sales	7,997,500	6,300,887	3,958,806
Costs of goods sold	7,065,982	5,625,221	3,559,730
Gross profit	931,518	675,666	399,076
Selling, general and administrative expenses	263,595	227,046	223,013
Profit sharing	43,149	25,476	2,980
Amortization of intangible assets	39,954	45,586	53,552
Impairment charges		12,805
Operating income	584,820	364,753	119,531
Interest expense, net of capitalized interest	176,977	170,229	141,360
Other income, net	(16,476)	(18,935)	(3,592)
Income (loss) before income taxes	424,319	213,459	(18,237)
Income taxes (benefit)	158,627	83,860	(7,218)
Net income (loss)	265,692	129,599	(11,019)
Net loss attributable to noncontrolling interests	12,428	11,110	2,835
Net income (loss) attributable to Steel Dynamics, Inc.	$ 278,120	$ 140,709	$ (8,184)
Basic earnings (loss) per share attributable to Steel Dynamics, Inc. stockholders (in dollars per share)	$ 1.27	$ 0.65	$ (0.04)
Weighted average common shares outstanding (in shares)	218,471	216,760	200,704
Diluted earnings (loss) per share attributable to Steel Dynamics, Inc. stockholders, including the effect of assumed conversions when dilutive (in dollars per share)	$ 1.22	$ 0.64	$ (0.04)
Weighted average common shares and share equivalents outstanding (in shares)	235,992	234,717	200,704
Dividends declared per share (in dollars per share)	$ 0.400	$ 0.300	$ 0.325