Customer Funds - Amortized Cost and Fair Value of Investment Security Available for Sale (Detail) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Investments Debt And Equity Securities [Abstract]
Due in one year or less, Cost	$ 3,670.5
Due in one to three years, Cost	724.4
Due in three to five years, Cost	811.9
Due after five years, Cost	271.7
Invested customer funds, Cost	5,478.5	$ 3,501.5
Due in one year or less, Fair Value	3,669.9
Due in one to three years, Fair Value	705.2
Due in three to five years, Fair Value	757.6
Due after five years, Fair Value	253.1
Invested customer funds, Fair Value	$ 5,385.8	$ 3,514.8