Other Operating Income - (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Components of Other Operating Income [Line Items]
Total Other Operating Income	$ 228.7	$ 191.3	$ 243.9
Other Operating Income	228.7	191.3	243.9
Loan Service Fees
Components of Other Operating Income [Line Items]
Total Other Operating Income	83.1	71.5	66.6
Banking Service Fees
Components of Other Operating Income [Line Items]
Total Other Operating Income	53.0	49.8	50.9
Bank Owned Life Insurance
Components of Other Operating Income [Line Items]
Other Operating Income	69.5	61.0	48.5
Other Income
Components of Other Operating Income [Line Items]
Total Other Operating Income	$ 23.1	$ 9.0	$ 77.9