Commitments and Contingencies - Additional Information (Detail) - USD ($)		3 Months Ended		9 Months Ended
	May 11, 2023	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Loss Contingencies [Line Items]
Commitments to extend credit to commercial customers		$ 12,500,000,000		$ 12,500,000,000		$ 11,700,000,000
Maximum credit risk for recourse associated with loans sold under Federal National Mortgage Association Delegated Underwriting and Servicing program		4,000,000,000		4,000,000,000		3,900,000,000
Estimate assessed losses	$ 15,800,000,000
Estimated uninsured deposits						$ 5,000,000,000
Annual special assessment rate	0.125%
Quarterly special assessment rate	0.0313%
FDIC assessments		29,364,000	$ 28,105,000	87,054,000	$ 66,266,000
FDIC estimated assessment				183,000,000
Minimum [Member]
Loss Contingencies [Line Items]
Range of reasonably possible losses		0		0
Maximum [Member]
Loss Contingencies [Line Items]
Range of reasonably possible losses		$ 25,000,000		$ 25,000,000