Other Operating Income - (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Components of Other Operating Income [Line Items]
Total Other Operating Income	$ 62.3	$ 53.5	$ 171.6	$ 144.4
Loan Service Fees
Components of Other Operating Income [Line Items]
Total Other Operating Income	16.1	13.6	49.3	37.3
Banking Service Fees
Components of Other Operating Income [Line Items]
Total Other Operating Income	12.6	11.8	37.8	34.1
Other Income
Components of Other Operating Income [Line Items]
Total Other Operating Income	$ 33.6	$ 28.1	$ 84.5	$ 73.0