Condensed Consolidated Statements of Shareholders' Equity - USD ($) shares in Millions, $ in Millions	Common Stock	Additional Paid In Capital	AOCI Attributable to Parent [Member]	Retained Earnings	Total
Balance at the beginning of the period at Dec. 31, 2022	$ 27.2	$ 290.4	$ (6.9)	$ 1,986.2	$ 2,296.9
Balance (in shares) at Dec. 31, 2022	36.3
Increase (Decrease) in Shareholders' Equity
Net income				34.0	34.0
Other comprehensive income (loss), net of tax			0.6		0.6
Share-based compensation		4.6			4.6
Shares issued, net of shares withheld for employee taxes	$ 0.2	(12.6)			(12.4)
Shares issued, net of shares withheld for employee taxes (in shares)	0.3
Shares repurchased	$ (0.5)	(2.7)		(38.9)	(42.1)
Shares repurchased (in shares)	(0.7)
Dividends				(11.3)	(11.3)
Balance at the end of the period at Mar. 31, 2023	$ 26.9	279.7	(6.3)	1,970.0	2,270.3
Balance (in shares) at Mar. 31, 2023	35.9
Balance at the beginning of the period at Dec. 31, 2023	$ 25.8	293.4	(8.2)	2,089.7	2,400.7
Balance (in shares) at Dec. 31, 2023	34.4
Increase (Decrease) in Shareholders' Equity
Net income				36.1	36.1
Other comprehensive income (loss), net of tax			(1.6)		(1.6)
Share-based compensation		5.7			5.7
Shares issued, net of shares withheld for employee taxes	$ 0.1	(17.3)			(17.2)
Shares issued, net of shares withheld for employee taxes (in shares)	0.2
Shares repurchased	$ (0.3)	(1.6)		(47.0)	$ (48.9)
Shares repurchased (in shares)	(0.4)				(0.4)
Equity interest in SSAT (see Note 4)				10.1	$ 10.1
Dividends				(11.1)	(11.1)
Balance at the end of the period at Mar. 31, 2024	$ 25.6	$ 280.2	$ (9.8)	$ 2,077.8	$ 2,373.8
Balance (in shares) at Mar. 31, 2024	34.2