CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Net sales
Unrelated parties	$ 1,728,401	$ 1,905,075
Related parties	67,295	76,965
Total net sales	1,795,696	1,982,040
Costs of goods sold	1,619,432	1,780,776
Gross profit	176,264	201,264
Selling, general and administrative expenses	65,262	64,384
Profit sharing	6,643	8,072
Amortization of intangible assets	8,127	8,992
Total selling, general and administrative expenses	80,032	81,448
Operating income	96,232	119,816
Interest expense, net of capitalized interest	34,629	41,112
Other expense (income), net	(1,046)	10,248
Income before income taxes	62,649	68,456
Income taxes	21,397	26,679
Net income	41,252	41,777
Net loss attributable to noncontrolling interests	6,963	3,898
Net income attributable to Steel Dynamics, Inc.	$ 48,215	$ 45,675
Basic earnings per share attributable to Steel Dynamics, Inc. stockholders (in dollars per share)	$ 0.22	$ 0.21
Weighted average common shares outstanding (in shares)	219,995	218,996
Diluted earnings per share attributable to Steel Dynamics, Inc. stockholders, including the effect of assumed conversions when dilutive (in dollars per share)	$ 0.21	$ 0.20
Weighted average common shares and share equivalents outstanding (in shares)	238,087	236,526
Dividends declared per share (in dollars per share)	$ 0.11	$ 0.10