Investment Securities - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2024 USD ($) positions	Dec. 31, 2023 USD ($) positions	Dec. 31, 2022 USD ($)
Schedule of Held-to-Maturity Securities [Line Items]
Investment securities - equity	$ 117.0	$ 126.0
Fair value gain (loss) adjustments, net	5.1	(1.3)
Fair value	$ 13,468.0	$ 11,165.0
Securities in unrealized loss position | positions	796	708
Provision for credit losses recognized	$ (1.0)	$ 18.5
Recognition of charge-off	0.0	17.1
Accrued interest receivable	5.0	5.0
Carrying value of securities sold	4,500.0	1,600.0	$ 170.0
Recognized net gains	17.4	(40.4)	$ 7.3
Asset Pledged as Collateral
Schedule of Held-to-Maturity Securities [Line Items]
Fair value	$ 4,000.0	$ 7,700.0