Senior Notes and Long-Term Debt - Senior Notes (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Senior Notes	$ 2,773.2	$ 2,724.2
Fixed Rate Due May 2027
Debt Instrument [Line Items]
Interest rate	4.00%
Senior Notes	$ 997.6	995.0
Fixed Rate Due Aug. 2028
Debt Instrument [Line Items]
Interest rate	3.65%
Senior Notes	$ 483.3	476.6
Fixed Rate Due May. 2029
Debt Instrument [Line Items]
Interest rate	3.15%
Senior Notes	$ 469.1	460.3
Fixed Rate Due May. 2030
Debt Instrument [Line Items]
Interest rate	1.95%
Senior Notes	$ 823.2	792.3
Senior Notes | Interest Rate Swaps
Debt Instrument [Line Items]
Change in unrealized gain (loss) on hedged item in fair value hedge	$ (219.1)	$ (264.7)