CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Net sales
Unrelated parties	$ 1,905,075	$ 1,941,664
Related parties	76,965	74,305
Total net sales	1,982,040	2,015,969
Costs of goods sold	1,780,776	1,720,215
Gross profit	201,264	295,754
Selling, general and administrative expenses	64,384	65,141
Profit sharing	8,072	15,203
Amortization of intangibles	8,992	10,084
Total selling, general and administrative expenses	81,448	90,428
Operating income	119,816	205,326
Interest expense, net of capitalized interest	41,112	43,346
Other expense (income), net	10,248	(4,567)
Income before income taxes	68,456	166,547
Income taxes	26,679	62,317
Net income	41,777	104,230
Net loss attributable to noncontrolling interests	3,898	1,673
Net income attributable to Steel Dynamics, Inc.	$ 45,675	$ 105,903
Basic earnings per share attributable to Steel Dynamics, Inc. stockholders (in dollars per share)	$ 0.21	$ 0.49
Weighted average common shares outstanding (in shares)	218,996	217,992
Diluted earnings per share attributable to Steel Dynamics, Inc. stockholders, including the effect of assumed conversions when dilutive (in dollars per share)	$ 0.20	$ 0.46
Weighted average common shares and share equivalents outstanding (in shares)	236,526	236,224
Dividends declared per share (in dollars per share)	$ 0.100	$ 0.100