CONSOLIDATED STATEMENTS OF COMPREHENSIVE (LOSS) INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 1,319.1	$ 371.4	$ (1,873.8)
Postretirement plans (net of $0.0 tax provisions in each period)	(53.8)	93.1	168.1
Foreign currency translation adjustment	(1.6)	(1.0)	6.1
Other comprehensive (loss) income, net of income taxes	(55.4)	92.1	174.2
Comprehensive income (loss)	1,263.7	463.5	(1,699.6)
Less: Net income (loss) attributable to noncontrolling interests	22.0	11.3	(3.5)
Comprehensive income (loss) attributable to common stockholders	$ 1,241.7	$ 452.2	$ (1,696.1)