Unaudited Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement of Comprehensive Income [Abstract]
Net (loss) income	$ (1,547.6)	$ 39.5	$ (1,679.1)	$ 169.4
Postretirement plans and workers’ compensation obligations (net of $0.0 tax provisions in each period)		(2.2)		(4.4)
Foreign currency translation adjustment	6.1	(0.5)	(0.7)	(0.4)
Other comprehensive income (loss), net of income taxes	3.9	(2.7)	(5.1)	(4.8)
Comprehensive (loss) income	(1,543.7)	36.8	(1,684.2)	164.6
Less: Net (loss) income attributable to noncontrolling interests	(3.4)	2.4	(5.2)	8.1
Comprehensive (loss) income attributable to common stockholders	$ (1,540.3)	$ 34.4	$ (1,679.0)	$ 156.5