Securities - Additional Information (Detail) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Schedule of Trading Securities and Other Trading Assets [Line Items]
Proceeds from sales of securities available for sale		$ 22,193,000	$ 0
Gross realized gains from securities	$ 154,000	154,000	0
Gross realized losses from securities		2,000	0
Accrued interest on securities available for sale	28,200,000	28,200,000		$ 32,100,000
Impairment on one corporate available-for-sale security		4,925,000
Sales of securities held to maturity		0	0
Amortized cost of available for sale securities transferred to held to maturity				4,100,000,000
Fair value of available for sale securities transferred to held to maturity				3,800,000,000
Gain (loss) on transfer of securities		0
Unamortized unrealized loss		216,500,000
Accrued interest on securities held to maturity	23,500,000	23,500,000		27,000,000
Unrealized gain (loss) on trading securities		(248,000)	$ 33,000
Securities sold not yet purchased	9,700,000	9,700,000		3,500,000
Visa Inc. [Member] | Class B Common Shares [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Pre-tax gain on sale of common shares		66,200,000
Collateral Dependent Assets [Member] | U.S. Government and Other Public Deposit [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Pledged securities for deposits	$ 8,500,000,000	$ 8,500,000,000		$ 10,300,000,000