CONSOLIDATED STATEMENTS OF SHAREHOLDERS’ EQUITY - USD ($) $ in Millions	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Income (Loss)
Balance (in shares) at Dec. 31, 2022		43,593,809			22,024,479
Balance at Dec. 31, 2022	$ 2,903.5	$ 0.4	$ 1,281.4	$ 2,610.1	$ (1,063.0)	$ 74.4
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	181.4			181.4
Change in fair value of cash flow swaps, net of reclassification adjustment	(14.6)					(14.6)
Unrealized gain on changes in fair value of debt securities, net of reclassification adjustment and tax expense	2.0					2.0
Comprehensive income	168.7			181.4		(12.6)
Share-based compensation	8.6		8.6
Issuance of common stock, net of forfeitures in connection with share-based payment arrangements (in shares)		(120,575)
Issuance of common stock, net of forfeitures, in connection with share-based payment arrangements	0.0
Repurchase of common stock associated with net share settlements of employee share-based awards (in shares)					45,613
Repurchase of common stock associated with net share settlement of employee share-based awards	(10.9)				$ (10.9)
Share issues (repurchases) (in shares)					110,323
Share repurchases	$ (20.7)				$ (20.7)
Retirement of common stock (in shares)	(110,323)	(164,527)			(164,527)
Retirement of common stock	$ 0.0		(2.0)	(28.2)	$ 30.2
Balance (in shares) at Mar. 31, 2023		43,549,857			22,015,888
Balance at Mar. 31, 2023	3,049.2	$ 0.4	1,288.0	2,763.3	$ (1,064.3)	61.8
Balance (in shares) at Dec. 31, 2023		42,352,001			22,018,537
Balance at Dec. 31, 2023	3,244.1	$ 0.4	1,288.4	2,961.5	$ (1,067.3)	61.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	147.1			147.1
Change in fair value of cash flow swaps, net of reclassification adjustment	7.5					7.5
Unrealized gain on changes in fair value of debt securities, net of reclassification adjustment and tax expense	(2.2)					(2.2)
Comprehensive income	152.4			147.1		5.3
Share-based compensation	10.5		10.5
Issuance of common stock, net of forfeitures in connection with share-based payment arrangements (in shares)		(123,845)
Issuance of common stock, net of forfeitures, in connection with share-based payment arrangements	0.0
Repurchase of common stock associated with net share settlements of employee share-based awards (in shares)					45,399
Repurchase of common stock associated with net share settlement of employee share-based awards	(9.8)				$ (9.8)
Share issues (repurchases) (in shares)					239,790
Share repurchases	$ (50.4)				$ (50.4)
Retirement of common stock (in shares)	(239,790)	(239,790)			(239,790)
Retirement of common stock	$ 0.0		(2.9)	(47.1)	$ 50.0
Balance (in shares) at Mar. 31, 2024		42,236,056			22,063,936
Balance at Mar. 31, 2024	$ 3,346.9	$ 0.4	$ 1,296.1	$ 3,061.5	$ (1,077.5)	$ 66.4