UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS’ EQUITY - USD ($) $ in Millions	Total	Common Stock	Additional paid-in capital	Retained earnings (Accumulated deficit)	Accumulated other comprehensive income	Noncontrolling interests	Treasury Stock, Common
Balance, beginning of period at Dec. 31, 2021		$ 1.8	$ 3,745.6	$ (913.2)	$ 297.9	$ 59.0	$ (1,370.3)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation for equity-classified awards			5.4
Common stock issuances, net of costs			221.9
Net income	$ 290.0			290.0		0.0
Dividends declared ($0.075, $0.000, $0.075, and $0.000 per share, respectively)				0.0
Repurchase of employee common stock relinquished for tax withholding	(2.6)						(2.6)
Postretirement plans (net of $0.0 tax provisions in each period)	(26.9)				(26.9)
Foreign currency translation adjustment	(1.5)				(1.5)
Distributions to noncontrolling interests						(13.8)
Common stock issuances, net of costs		0.1
Balance, end of period at Jun. 30, 2022	2,293.4	1.9	3,972.9	(623.2)	269.5	45.2	(1,372.9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock repurchases	0.0						0.0
Unsettled common stock repurchases							0.0
Dividend equivalent units on dividends declared			0.0
Sales and Excise Tax Payable							0.0
Balance, beginning of period at Mar. 31, 2022		1.9	3,969.5	(1,032.7)	286.4	44.1	(1,372.3)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation for equity-classified awards			3.4
Common stock issuances, net of costs			0.0
Net income	410.6			409.5		1.1
Dividends declared ($0.075, $0.000, $0.075, and $0.000 per share, respectively)				0.0
Repurchase of employee common stock relinquished for tax withholding							(0.6)
Postretirement plans (net of $0.0 tax provisions in each period)	(13.5)				(13.5)
Foreign currency translation adjustment	(3.4)				(3.4)
Distributions to noncontrolling interests						0.0
Common stock issuances, net of costs		0.0
Balance, end of period at Jun. 30, 2022	2,293.4	1.9	3,972.9	(623.2)	269.5	45.2	(1,372.9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock repurchases							0.0
Unsettled common stock repurchases							0.0
Dividend equivalent units on dividends declared			0.0
Sales and Excise Tax Payable							0.0
Balance, beginning of period at Dec. 31, 2022	3,294.8	1.9	3,975.9	383.9	242.5	63.5	(1,372.9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation for equity-classified awards			3.4
Common stock issuances, net of costs			0.0
Net income	485.6			447.7		37.9
Dividends declared ($0.075, $0.000, $0.075, and $0.000 per share, respectively)				(10.9)
Repurchase of employee common stock relinquished for tax withholding	(13.7)						(13.7)
Postretirement plans (net of $0.0 tax provisions in each period)	(26.8)				(26.8)
Foreign currency translation adjustment	(0.6)				(0.6)
Distributions to noncontrolling interests						(22.8)
Common stock issuances, net of costs		0.0
Balance, end of period at Jun. 30, 2023	3,523.3	1.9	3,979.4	820.7	215.1	78.6	(1,572.4)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock repurchases	173.0						(173.0)
Unsettled common stock repurchases							(11.2)
Dividend equivalent units on dividends declared			0.1
Sales and Excise Tax Payable							(1.6)
Balance, beginning of period at Mar. 31, 2023		1.9	3,977.6	652.4	228.9	55.0	(1,386.1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation for equity-classified awards			1.7
Common stock issuances, net of costs			0.0
Net income	202.8			179.2		23.6
Dividends declared ($0.075, $0.000, $0.075, and $0.000 per share, respectively)				(10.9)
Repurchase of employee common stock relinquished for tax withholding							(0.5)
Postretirement plans (net of $0.0 tax provisions in each period)	(13.4)				(13.4)
Foreign currency translation adjustment	(0.4)				(0.4)
Distributions to noncontrolling interests						0.0
Common stock issuances, net of costs		0.0
Balance, end of period at Jun. 30, 2023	$ 3,523.3	$ 1.9	3,979.4	$ 820.7	$ 215.1	$ 78.6	(1,572.4)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock repurchases							(173.0)
Unsettled common stock repurchases							(11.2)
Dividend equivalent units on dividends declared			$ 0.1
Sales and Excise Tax Payable							$ (1.6)