Condensed Consolidated Statements of Shareholders' Equity - USD ($) shares in Millions, $ in Millions	Common Stock	Additional Paid In Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Total
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)
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
Balance at the beginning of the period at Dec. 31, 2024	$ 24.7	296.7	(6.5)	2,337.1	2,652.0
Balance (in shares) at Dec. 31, 2024	33.0
Increase (Decrease) in Shareholders' Equity
Net income				72.3	72.3
Other comprehensive income (loss), net of tax			(0.3)		(0.3)
Share-based compensation		5.8			5.8
Shares issued, net of shares withheld for employee taxes	$ 0.1	(16.2)			(16.1)
Shares issued, net of shares withheld for employee taxes (in shares)	0.1
Shares repurchased	$ (0.3)	(1.6)		(67.3)	(69.2)
Shares repurchased (in shares)	(0.5)
Dividends				(11.3)	(11.3)
Balance at the end of the period at Mar. 31, 2025	$ 24.5	$ 284.7	$ (6.8)	$ 2,330.8	$ 2,633.2
Balance (in shares) at Mar. 31, 2025	32.6