CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net sales
Unrelated parties	$ 7,407,233	$ 8,481,567	$ 7,087,101
Related parties	187,178	274,385	285,823
Total net sales	7,594,411	8,755,952	7,372,924
Costs of goods sold	6,862,693	7,789,741	6,653,780
Gross profit	731,718	966,211	719,144
Selling, general and administrative expenses	327,626	316,214	272,777
Profit sharing	23,064	42,126	27,764
Amortization of intangible assets	25,312	27,551	31,770
Impairment charges	428,500	260,000	308
Operating income (loss)	(72,784)	320,320	386,525
Interest expense, net of capitalized interest	153,950	137,263	127,728
Other (income) expense, net	15,383	18,254	(4,033)
Income (loss) before income taxes	(242,117)	164,803	262,830
Income tax expense (benefit)	(96,947)	73,153	99,314
Net income (loss)	(145,170)	91,650	163,516
Net loss attributable to noncontrolling interests	14,859	65,374	25,798
Net income (loss) attributable to Steel Dynamics, Inc.	$ (130,311)	$ 157,024	$ 189,314
Basic earnings (loss) per share attributable to Steel Dynamics, Inc. stockholders (in dollars per share)	$ (0.54)	$ 0.68	$ 0.86
Weighted average common shares outstanding - basic (in shares)	242,017	232,547	220,916
Diluted earnings (loss) per share attributable to Steel Dynamics, Inc. stockholders, including the effect of assumed conversions when dilutive (in dollars per share)	$ (0.54)	$ 0.67	$ 0.83
Weighted average common shares and share equivalents outstanding (in shares)	242,017	242,078	238,996
Dividends declared per share (in dollars per share)	$ 0.55	$ 0.46	$ 0.44