Securities - Additional Information (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2023 USD ($) holding	Jun. 30, 2022 USD ($)	Jun. 30, 2023 USD ($) holding	Jun. 30, 2022 USD ($)	Dec. 31, 2022 USD ($) holding
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, allowance for credit loss, excluding accrued interest	$ 0	$ 0	$ 0	$ 0	$ 0
Debt securities, available-for-sale, accrued interest, after allowance for credit loss	9,800,000		9,800,000		$ 12,900,000
Debt securities, available-for-sale, accrued interest writeoff	$ 0	0	$ 0	0
Number of securities in an unrealized loss position | holding	775		775		802
Debt securities, held-to-maturity, allowance for credit loss, excluding accrued interest	$ 0	0	$ 0	0	$ 0
Debt securities, held-to-maturity, accrued interest, after allowance for credit loss	1,000,000		1,000,000		1,000,000
Debt securities, held-to-maturity, accrued interest, writeoff	0	$ 0	0	$ 0
Deposit liabilities, collateral issued, financial instruments	446,400,000		446,400,000		437,900,000
Other debt securities
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, allowance for credit loss, excluding accrued interest	0		0		$ 0
Number of securities in an unrealized loss position | holding					2
Foreign Debt Securities
Debt Securities, Available-for-sale [Line Items]
Number of securities in an unrealized loss position | holding					2
Bank Term Funding Program
Debt Securities, Available-for-sale [Line Items]
Deposit liabilities, collateral issued, financial instruments	2,500,000,000		2,500,000,000		$ 0
Federal Reserve Discount Window
Debt Securities, Available-for-sale [Line Items]
Deposit liabilities, collateral issued, financial instruments	$ 374,900,000		$ 374,900,000		$ 0