CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Net sales
Unrelated parties	$ 2,092,964	$ 2,766,364	$ 4,664,508	$ 5,580,850
Related parties	1,341	4,151	4,897	7,100
Total net sales	2,094,305	2,770,515	4,669,405	5,587,950
Costs of goods sold	1,809,874	2,349,349	3,969,745	4,733,214
Gross profit	284,431	421,166	699,660	854,736
Selling, general and administrative expenses	109,299	106,250	222,197	217,288
Profit sharing	9,092	22,871	30,546	46,548
Amortization of intangible assets	7,190	7,013	14,381	14,026
Operating income	158,850	285,032	432,536	576,874
Interest expense, net of capitalized interest	27,702	32,321	55,721	63,443
Other (income) expense, net	28,103	(4,249)	25,514	(10,592)
Income before income taxes	103,045	256,960	351,301	524,023
Income tax expense	24,280	60,214	81,700	122,450
Net income	78,765	196,746	269,601	401,573
Net income attributable to noncontrolling interests	(3,269)	(2,444)	(6,765)	(2,943)
Net income attributable to Steel Dynamics, Inc.	$ 75,496	$ 194,302	$ 262,836	$ 398,630
Basic earnings per share attributable to Steel Dynamics, Inc. stockholders	$ 0.36	$ 0.88	$ 1.24	$ 1.79
Weighted average common shares outstanding (in shares)	210,343	221,505	211,798	222,781
Diluted earnings per share attributable to Steel Dynamics, Inc. stockholders, including the effect of assumed conversions when dilutive (in dollars per share)	$ 0.36	$ 0.87	$ 1.24	$ 1.78
Weighted average common shares and share equivalents outstanding (in shares)	211,378	222,519	212,701	223,741
Dividends declared per share (in dollars per share)	$ 0.25	$ 0.24	$ 0.50	$ 0.48