Consolidated Statements of Comprehensive (Loss) Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net (loss) income	$ (1.4)	$ (163.1)	$ 12.3	$ (147.6)
Other comprehensive (loss) income:
Reclassifications of prior service benefit and actuarial benefit amortization to earnings, net of tax	0.1	0.0	0.1	0.0
Currency translation adjustment	(0.4)	(0.9)	(1.9)	(0.8)
Comprehensive (loss) income	(1.7)	(164.0)	10.5	(148.4)
Less: Comprehensive income (loss) attributable to noncontrolling interests	1.3	(0.1)	3.6	3.3
Comprehensive (loss) income attributable to SunCoke Energy, Inc.	$ (3.0)	$ (163.9)	$ 6.9	$ (151.7)