CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Net sales
Unrelated parties	$ 2,597,312	$ 2,319,663
Related parties	6,563	48,553
Total net sales	2,603,875	2,368,216
Costs of goods sold	2,140,459	1,896,062
Gross profit	463,416	472,154
Selling, general and administrative expenses	106,431	102,933
Profit sharing	26,662	27,231
Amortization of intangible assets	6,926	7,424
Operating income	323,397	334,566
Interest expense, net of capitalized interest	31,896	33,973
Other expense (income), net	(4,463)	(3,659)
Income before income taxes	295,964	304,252
Income tax expense	70,489	105,586
Net income	225,475	198,666
Net loss attributable to noncontrolling interests	2,076	2,151
Net income attributable to Steel Dynamics, Inc.	$ 227,551	$ 200,817
Basic earnings per share attributable to Steel Dynamics, Inc. stockholders	$ 0.96	$ 0.83
Weighted average common shares outstanding - basic (in shares)	236,623	242,943
Diluted earnings per share attributable to Steel Dynamics, Inc. stockholders, including the effect of assumed conversions when dilutive (in dollars per share)	$ 0.96	$ 0.82
Weighted average common shares and share equivalents outstanding (in shares)	237,723	244,546
Dividends declared per share (in dollars per share)	$ 0.1875	$ 0.155