Reporting Segments and Related Information - Narrative (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2024 USD ($) location segment	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment	2
Net interest income	$ 2,177.1	$ 1,982.0	$ 1,887.2
Segment reporting information, fully taxable-equivalent adjustment	31.8	$ 57.5	$ 45.6
Asset Servicing segment | Change in allocation of net interest income
Segment Reporting Information [Line Items]
Net interest income	$ (132.0)
Wealth Management segment
Segment Reporting Information [Line Items]
Services provided by business units, states | location	19
Wealth Management segment | Change in allocation of net interest income
Segment Reporting Information [Line Items]
Net interest income	$ 132.0