UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS’ EQUITY - USD ($) $ in Millions	Total	Common Stock	Additional paid-in capital	Retained earnings	Accumulated other comprehensive income	Noncontrolling interests	Treasury Stock, Common
Balance, beginning of period at Dec. 31, 2022		$ 1.9	$ 3,975.9	$ 383.9	$ 242.5	$ 63.5	$ (1,372.9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividend equivalent units on dividends declared			0.0
Share-based compensation for equity-classified awards			1.7
Net income	$ 282.8			268.5		14.3
Dividends declared ($0.075 and $0.000 per share, respectively)				0.0
Common stock repurchases	0.0						0.0
Unsettled common stock repurchases							0.0
Sales and Excise Tax Payable							0.0
Repurchase of employee common stock relinquished for tax withholding	(13.2)						(13.2)
Postretirement plans (net of $0.0 tax provisions in each period)	(13.4)				(13.4)
Foreign currency translation adjustment	(0.2)				(0.2)
Distributions to noncontrolling interests						(22.8)
Balance, end of period at Mar. 31, 2023	3,529.7	1.9	3,977.6	652.4	228.9	55.0	(1,386.1)
Balance, beginning of period at Dec. 31, 2023	3,607.5	1.9	3,983.0	1,112.7	189.6	60.5	(1,740.2)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividend equivalent units on dividends declared			0.1
Share-based compensation for equity-classified awards			2.0
Net income	45.0			39.6		5.4
Dividends declared ($0.075 and $0.000 per share, respectively)				(9.8)
Common stock repurchases	83.1						(83.1)
Unsettled common stock repurchases							2.6
Sales and Excise Tax Payable							(0.7)
Repurchase of employee common stock relinquished for tax withholding	(3.4)						(3.4)
Postretirement plans (net of $0.0 tax provisions in each period)	(13.2)				(13.2)
Foreign currency translation adjustment	(1.9)				(1.9)
Distributions to noncontrolling interests						(18.5)
Balance, end of period at Mar. 31, 2024	$ 3,526.6	$ 1.9	$ 3,985.1	$ 1,142.5	$ 174.5	$ 47.4	$ (1,824.8)