CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME
Net income	$ 570,828	$ 677,900	$ 1,255,805
Other comprehensive income (loss) - net unrealized gain (loss) on cash flow hedging derivatives, net of income tax expense of $594, income tax benefit of $96, and income tax expense of $94 for 2020, 2019 and 2018, respectively	1,909	(308)	301
Comprehensive income	572,737	677,592	1,256,106
Comprehensive (income) loss attributable to noncontrolling interests	(20,006)	(6,797)	2,574
Comprehensive income attributable to Steel Dynamics, Inc.	$ 552,731	$ 670,795	$ 1,258,680