Other Operating Income - (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Components of Other Operating Income [Line Items]
Other operating income	$ 61.0	$ 46.8
Loan Service Fees
Components of Other Operating Income [Line Items]
Other operating income	15.7	18.7
Banking Service Fees
Components of Other Operating Income [Line Items]
Other operating income	13.3	12.2
Bank Owned Life Insurance
Components of Other Operating Income [Line Items]
Other operating income	20.6	16.7
Other Income
Components of Other Operating Income [Line Items]
Other operating income	$ 11.4	$ (0.8)