Income Tax Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2018
Federal Income Tax Note
Less Tax Attributable to Temporary Items Included Above	$ (21.2)	$ (42.4)	$ (63.5)
Unrecognized Tax Benefits, Interest on Income Taxes Expense	13.2	12.2	7.8
Unrecognized Tax Benefits, Interest on Income Taxes Accrued	59.4	46.2	34.0
Operating Loss Carryforwards	0.0
Valuation Allowance on Deferred Tax Assets	12.1	11.0
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	1.1	0.7
Income Taxes Paid, Net	376.0	$ 446.0	$ 375.0
Tax Year 2017
Federal Income Tax Note
Increases for Tax Positions Related to Prior Years				$ 261.1
State and Local Jurisdiction
Federal Income Tax Note
Operating Loss Carryforwards	$ 182.9