CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net sales
Unrelated parties	$ 9,587,691	$ 10,451,132	$ 11,801,609
Related parties	13,791	13,859	20,230
Total net sales	9,601,482	10,464,991	11,821,839
Costs of goods sold	8,166,754	8,934,007	9,499,025
Gross profit	1,434,728	1,530,984	2,322,814
Selling, general and administrative expenses	477,450	436,498	416,640
Profit sharing	61,728	78,029	155,985
Amortization of intangible assets	28,999	29,577	27,780
Asset impairment charges	19,409
Operating income	847,142	986,880	1,722,409
Interest expense, net of capitalized interest	94,877	127,104	126,620
Other (income) expense, net	46,787	(15,561)	(23,985)
Income before income taxes	705,478	875,337	1,619,774
Income tax expense	134,650	197,437	363,969
Net income	570,828	677,900	1,255,805
Net (income) loss attributable to noncontrolling interests	(20,006)	(6,797)	2,574
Net income attributable to Steel Dynamics, Inc.	$ 550,822	$ 671,103	$ 1,258,379
Basic earnings per share attributable to Steel Dynamics, Inc. stockholders (in dollars per share)	$ 2.61	$ 3.06	$ 5.38
Weighted average common shares outstanding (in shares)	211,140	219,639	233,923
Diluted earnings per share attributable to Steel Dynamics, Inc. stockholders, including the effect of assumed conversions when dilutive (in dollars per share)	$ 2.59	$ 3.04	$ 5.35
Weighted average common shares and share equivalents outstanding (in shares)	212,345	220,748	235,193
Dividends declared per share (in dollars per share)	$ 1.00	$ 0.96	$ 0.75