Securities - Additional Information (Detail) - USD ($)	3 Months Ended	6 Months Ended	9 Months Ended
	Sep. 30, 2021	Jun. 30, 2022	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Schedule of Trading Securities and Other Trading Assets [Line Items]
Proceeds from sales of securities available for sale			$ 0	$ 295,546,000
Gross realized gains from securities	$ 1,060,000		0	5,080,000
Gross realized losses from securities	$ 2,000		0	2,300
Accrued interest on securities available for sale			28,300,000		$ 45,800,000
Sales of securities held to maturity			0	0
Amortized cost of available for sale securities transferred to held to maturity			4,000,000,000.0
Fair value of available for sale securities transferred to held to maturity			3,700,000,000
Gain (loss) on transfer of securities			0
Unamortized unrealized loss			235,200,000
Accrued interest on securities held to maturity			22,600,000		5,300,000
Unrealized gain (loss) on trading securities			33,000	$ (154,000)
Securities sold not yet purchased			4,000,000.0		3,200,000
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			9,400,000,000		10,200,000,000
Collateral Dependent Assets [Member] | Federal Reserve Discount Window [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Pledged securities for deposits			$ 129,900,000		$ 171,200,000