CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Net sales
Unrelated parties	$ 7,007,417	$ 7,718,714	$ 6,060,933
Related parties	282,817	278,786	239,954
Total net sales	7,290,234	7,997,500	6,300,887
Costs of goods sold	6,570,336	7,065,982	5,625,221
Gross profit	719,898	931,518	675,666
Selling, general and administrative expenses	257,943	263,595	227,046
Profit sharing	26,987	43,149	25,476
Amortization of intangible assets	35,553	39,954	45,586
Impairment charges	8,250		12,805
Operating income	391,165	584,820	364,753
Interest expense, net of capitalized interest	158,585	176,977	170,229
Other (income) expense, net	28,514	(16,476)	(18,935)
Income before income taxes	204,066	424,319	213,459
Income taxes	61,785	158,627	83,860
Net income	142,281	265,692	129,599
Net loss attributable to noncontrolling interests	21,270	12,428	11,110
Net income attributable to Steel Dynamics, Inc.	$ 163,551	$ 278,120	$ 140,709
Basic earnings per share attributable to Steel Dynamics, Inc. stockholders (in dollars per share)	$ 0.75	$ 1.27	$ 0.65
Weighted average common shares outstanding (in shares)	219,159	218,471	216,760
Diluted earnings per share attributable to Steel Dynamics, Inc. stockholders, including the effect of assumed conversions when dilutive (in dollars per share)	$ 0.73	$ 1.22	$ 0.64
Weighted average common shares and share equivalents outstanding (in shares)	236,624	235,992	234,717
Dividends declared per share (in dollars per share)	$ 0.40	$ 0.40	$ 0.30