CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Net sales
Unrelated parties	$ 1,735,420	$ 1,830,117	$ 3,463,821	$ 3,735,192
Related parties	65,920	79,686	133,215	156,651
Total net sales	1,801,340	1,909,803	3,597,036	3,891,843
Costs of goods sold	1,653,648	1,727,667	3,273,080	3,508,443
Gross profit	147,692	182,136	323,956	383,400
Selling, general and administrative expenses	65,356	61,235	130,618	125,619
Profit sharing	4,779	8,211	11,422	16,283
Amortization of intangible assets	8,051	8,991	16,178	17,983
Impairment charges	308		308
Total selling, general and administrative expenses	78,494	78,437	158,526	159,885
Operating income	69,198	103,699	165,430	223,515
Interest expense, net of capitalized interest	31,465	41,106	66,094	82,218
Other expense (income), net	(1,246)	(1,892)	(2,292)	8,356
Income before income taxes	38,979	64,485	101,628	132,941
Income taxes	15,706	25,180	37,103	51,859
Net income	23,273	39,305	64,525	81,082
Net loss attributable to noncontrolling interests	5,685	5,167	12,648	9,065
Net income attributable to Steel Dynamics, Inc.	$ 28,958	$ 44,472	$ 77,173	$ 90,147
Basic earnings per share attributable to Steel Dynamics, Inc. stockholders (in dollars per share)	$ 0.13	$ 0.20	$ 0.35	$ 0.41
Weighted average common shares outstanding (in shares)	220,471	219,104	220,233	219,050
Diluted earnings per share attributable to Steel Dynamics, Inc. stockholders, including the effect of assumed conversions when dilutive (in dollars per share)	$ 0.13	$ 0.20	$ 0.34	$ 0.40
Weighted average common shares and share equivalents outstanding (in shares)	221,736	236,208	238,246	236,367
Dividends declared per share (in dollars per share)	$ 0.11	$ 0.10	$ 0.22	$ 0.20