Loans - Summary of Nonaccrual Loans and Accruing Receivables 90 Days or More Delinquent (Detail) - USD ($) $ in Millions	3 Months Ended
Jun. 30, 2022	Dec. 31, 2021
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans	$ 515	$ 617
Accruing Loans Contractually Past Due 90 Days or More	2	3
Nonaccrual Loans With No Allowance For Credit Losses	221	211
Residential mortgage loans carried at lower of cost or fair value of the collateral less cost to sell	95	86
Commercial loans
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans	308	379
Accruing Loans Contractually Past Due 90 Days or More	1	1
Nonaccrual Loans With No Allowance For Credit Losses	152	152
Commercial loans \| Real estate, including construction
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans	94	140
Accruing Loans Contractually Past Due 90 Days or More	0	0
Nonaccrual Loans With No Allowance For Credit Losses	18	20
Commercial loans \| Business and corporate banking
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans	122	134
Accruing Loans Contractually Past Due 90 Days or More	1	1
Nonaccrual Loans With No Allowance For Credit Losses	64	69
Commercial loans \| Global banking
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans	92	105
Accruing Loans Contractually Past Due 90 Days or More	0	0
Nonaccrual Loans With No Allowance For Credit Losses	70	63
Consumer loans
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans	207	238
Accruing Loans Contractually Past Due 90 Days or More	1	2
Nonaccrual Loans With No Allowance For Credit Losses	69	59
Transfer of loans held-for-sale to held-for-investment	538
Consumer loans \| Nonperforming Financial Instruments
Financing Receivable, Past Due [Line Items]
Transfer of loans held-for-sale to held-for-investment	63
Consumer loans \| Residential mortgages
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans	198	229
Accruing Loans Contractually Past Due 90 Days or More	0	0
Nonaccrual Loans With No Allowance For Credit Losses	64	55
Consumer loans \| Home equity mortgages
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans	9	9
Accruing Loans Contractually Past Due 90 Days or More	0	0
Nonaccrual Loans With No Allowance For Credit Losses	5	4
Consumer loans \| Credit cards
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans	0	0
Accruing Loans Contractually Past Due 90 Days or More	1	2
Nonaccrual Loans With No Allowance For Credit Losses	$ 0	$ 0

Residential Mortgage Loan Nonaccrual Carried At Lower Of Amortized Cost Or Fair Value Less Cost To Sell

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- Definition

Amortized cost excluding accrued interest, of financing receivable 90 days or more past due and still accruing. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 16
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919258-210447

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- Definition

Amortized cost excluding accrued interest, of financing receivable on nonaccrual status. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 16
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919258-210447

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- Definition

Amortized cost excluding accrued interest, of financing receivable on nonaccrual status with no allowance for credit loss. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 16
-Subparagraph (d)
-URI https://asc.fasb.org/extlink&oid=124255953&loc=SL82919258-210447

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+ References

No definition available.

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- Definition

Value of loans held-for-sale transferred to loans held in the entity's portfolio in noncash transactions.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
-URI https://asc.fasb.org/extlink&oid=126999549&loc=d3e4304-108586

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-Topic 230
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