Other Operating Income - (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Components of Other Operating Income [Line Items]
Other operating income	$ 46.8	$ 41.1
Loan Service Fees
Components of Other Operating Income [Line Items]
Other operating income	18.7	16.7
Banking Service Fees
Components of Other Operating Income [Line Items]
Other operating income	12.2	12.7
Bank Owned Life Insurance
Components of Other Operating Income [Line Items]
Other operating income	16.7	11.8
Other Income
Components of Other Operating Income [Line Items]
Other operating income	$ (0.8)	$ (0.1)