CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME
Net income	$ 677,900	$ 1,255,805	$ 805,796
Other comprehensive income (loss) - net unrealized gain (loss) on cash flow hedging derivatives, net of income tax benefit of $96 and income tax expense of $94 for 2019 and 2018, respectively	(308)	301
Comprehensive income	677,592	1,256,106	805,796
Comprehensive (income) loss attributable to noncontrolling interests	(6,797)	2,574	6,945
Comprehensive income attributable to Steel Dynamics, Inc.	$ 670,795	$ 1,258,680	$ 812,741