Other Operating Income - (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Components of Other Operating Income [Line Items]
Total Other Operating Income	$ 194.0	$ 145.5	$ 127.5
Loan Service Fees
Components of Other Operating Income [Line Items]
Total Other Operating Income	52.5	48.0	48.9
Banking Service Fees
Components of Other Operating Income [Line Items]
Total Other Operating Income	46.1	45.6	46.4
Other Income
Components of Other Operating Income [Line Items]
Total Other Operating Income	$ 95.4	$ 51.9	$ 32.2