CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Net sales
Unrelated parties	$ 1,624,561	$ 1,976,296	$ 5,359,753	$ 5,922,243
Related parties	68,829	67,159	225,480	216,912
Total net sales	1,693,390	2,043,455	5,585,233	6,139,155
Costs of goods sold	1,536,989	1,844,212	5,045,432	5,367,772
Gross profit	156,401	199,243	539,801	771,383
Selling, general and administrative expenses	62,984	72,876	188,603	201,648
Profit sharing	3,954	7,428	20,237	37,085
Amortization of intangible assets	8,848	10,154	26,831	30,320
Impairment charges	7,894		7,894
Total selling, general and administrative expenses	83,680	90,458	243,565	269,053
Operating income	72,721	108,785	296,236	502,330
Interest expense, net of capitalized interest	41,490	44,702	123,708	132,860
Other expense (income), net	24,010	(3,523)	32,366	(13,835)
Income before income taxes	7,221	67,606	140,162	383,305
Income taxes	1,116	27,749	52,975	143,392
Net income	6,105	39,857	87,187	239,913
Net loss attributable to noncontrolling interests	6,728	3,447	15,793	8,004
Net income attributable to Steel Dynamics, Inc.	$ 12,833	$ 43,304	$ 102,980	$ 247,917
Basic earnings per share attributable to Steel Dynamics, Inc. stockholders (in dollars per share)	$ 0.06	$ 0.20	$ 0.47	$ 1.14
Weighted average common shares outstanding (in shares)	219,191	218,674	219,097	218,389
Diluted earnings per share attributable to Steel Dynamics, Inc. stockholders, including the effect of assumed conversions when dilutive (in dollars per share)	$ 0.06	$ 0.19	$ 0.47	$ 1.08
Weighted average common shares and share equivalents outstanding (in shares)	220,044	235,759	236,536	236,083
Dividends declared per share (in dollars per share)	$ 0.10	$ 0.10	$ 0.30	$ 0.30