CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Net sales
Unrelated parties	$ 1,838,464	$ 1,624,561	$ 5,302,285	$ 5,359,753
Related parties	73,274	68,829	206,489	225,480
Total net sales	1,911,738	1,693,390	5,508,774	5,585,233
Costs of goods sold	1,714,546	1,536,989	4,987,626	5,045,432
Gross profit	197,192	156,401	521,148	539,801
Selling, general and administrative expenses	67,553	62,984	198,171	188,603
Profit sharing	8,469	3,954	19,891	20,237
Amortization of intangible assets	7,897	8,848	24,075	26,831
Impairment charges		7,894	308	7,894
Total selling, general and administrative expenses	83,919	83,680	242,445	243,565
Operating income	113,273	72,721	278,703	296,236
Interest expense, net of capitalized interest	30,970	41,490	97,064	123,708
Other expense (income), net	(1,852)	24,010	(4,144)	32,366
Income before income taxes	84,155	7,221	185,783	140,162
Income taxes	33,065	1,116	70,168	52,975
Net income	51,090	6,105	115,615	87,187
Net loss attributable to noncontrolling interests	6,396	6,728	19,044	15,793
Net income attributable to Steel Dynamics, Inc.	$ 57,486	$ 12,833	$ 134,659	$ 102,980
Basic earnings per share attributable to Steel Dynamics, Inc. stockholders (in dollars per share)	$ 0.26	$ 0.06	$ 0.61	$ 0.47
Weighted average common shares outstanding (in shares)	220,926	219,191	220,464	219,097
Diluted earnings per share attributable to Steel Dynamics, Inc. stockholders, including the effect of assumed conversions when dilutive (in dollars per share)	$ 0.25	$ 0.06	$ 0.59	$ 0.47
Weighted average common shares and share equivalents outstanding (in shares)	239,001	220,044	238,497	236,536
Dividends declared per share (in dollars per share)	$ 0.11	$ 0.10	$ 0.33	$ 0.30