UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Statement of Comprehensive Income [Abstract]
Net income	$ 45.0	$ 282.8
Postretirement plans (net of $0.0 tax provisions in each period)	(13.2)	(13.4)
Foreign currency translation adjustment	(1.9)	(0.2)
Other comprehensive loss, net of income taxes	(15.1)	(13.6)
Comprehensive income	29.9	269.2
Less: Net income attributable to noncontrolling interests	5.4	14.3
Comprehensive income attributable to common stockholders	$ 24.5	$ 254.9