Securities - Additional Information (Detail) - USD ($)	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Securities available-for-sale, allowance for credit losses	$ 1,000,000	$ 1,000,000
Securities held-to-maturity, allowance for credit losses	1,000,000	2,000,000
Securities held-to-maturity, nonaccrual	0	0
Equity securities without readily determinable fair values, impairment loss adjustment	3,000,000	2,000,000	$ 0
Financial Asset, Past Due
Debt Securities, Available-for-sale [Line Items]
Securities held-to-maturity, past due	0	0
Other assets:
Debt Securities, Available-for-sale [Line Items]
Federal Home Loan Bank stock	110,000,000	259,000,000
Federal Reserve Bank stock	$ 558,000,000	$ 559,000,000

Amount excluding accrued interest, of allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454

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Amount, excluding accrued interest, of allowance for credit loss on investment in debt security measured at amortized cost (held-to-maturity).

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-Publisher FASB
-Name Accounting Standards Codification
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Federal Home Loan Bank (FHLB) stock represents an equity interest in a FHLB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity).

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Federal Reserve Bank stock represents an equity interest in the Federal Reserve Bank. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity).

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Amount, before allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity).

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