Income Taxes - Components of Income Tax Expense (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Provision for current income taxes
Federal	$ 103.8	$ 94.1	$ 81.3
State	37.4	31.9	30.1
Total provision for current income taxes	141.2	126.0	111.4
Provision for deferred income taxes
Federal	3.9	5.4	(2.8)
State	1.9	0.2	(0.4)
Total provision for deferred income taxes	5.8	5.6	(3.2)
Total provision for income taxes	$ 147.0	$ 131.6	$ 108.2