Unaudited Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net (loss) income	$ (78.1)	$ 79.8	$ 91.3	$ 403.2
Postretirement plans and workers’ compensation obligations (net of $0.0 tax provisions in each period)	(2.2)	0.0	(6.6)	0.0
Foreign currency translation adjustment	(1.3)	(1.5)	(1.7)	(4.5)
Other comprehensive loss, net of income taxes	(3.5)	(1.5)	(8.3)	(4.5)
Comprehensive (loss) income	(81.6)	78.3	83.0	398.7
Less: Series A Convertible Preferred Stock dividends	0.0	0.0	0.0	102.5
Less: Net income attributable to noncontrolling interests	4.7	8.3	12.8	8.9
Comprehensive (loss) income attributable to common stockholders	$ (86.3)	$ 70.0	$ 70.2	$ 287.3