UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Statement of Comprehensive Income [Abstract]
Net loss	$ (120.6)	$ (79.7)
Postretirement plans (net of $0.0 tax provisions in each period)	(13.4)	(11.0)
Foreign currency translation adjustment	1.9	(0.2)
Other comprehensive loss, net of income taxes	(11.5)	(11.2)
Comprehensive loss	(132.1)	(90.9)
Less: Net (loss) income attributable to noncontrolling interests	(1.1)	0.4
Comprehensive loss attributable to common stockholders	$ (131.0)	$ (91.3)