Loans - Summary of Nonaccrual Loans and Accruing Receivables 90 Days or More Delinquent (Detail) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2022	Sep. 30, 2022	Dec. 31, 2021
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans		$ 548	$ 617
Accruing Loans Contractually Past Due 90 Days or More		2	3
Nonaccrual Loans With No Allowance For Credit Losses		259	211
Residential mortgage loans carried at lower of cost or fair value of the collateral less cost to sell		102	86
Commercial loans
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans		342	379
Accruing Loans Contractually Past Due 90 Days or More		1	1
Nonaccrual Loans With No Allowance For Credit Losses		183	152
Commercial loans | Real estate, including construction
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans		136	140
Accruing Loans Contractually Past Due 90 Days or More		0	0
Nonaccrual Loans With No Allowance For Credit Losses		61	20
Commercial loans | Business and corporate banking
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans		119	134
Accruing Loans Contractually Past Due 90 Days or More		1	1
Nonaccrual Loans With No Allowance For Credit Losses		49	69
Commercial loans | Global banking
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans		87	105
Accruing Loans Contractually Past Due 90 Days or More		0	0
Nonaccrual Loans With No Allowance For Credit Losses		73	63
Consumer loans
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans		206	238
Accruing Loans Contractually Past Due 90 Days or More		1	2
Nonaccrual Loans With No Allowance For Credit Losses		76	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		199	229
Accruing Loans Contractually Past Due 90 Days or More		0	0
Nonaccrual Loans With No Allowance For Credit Losses		71	55
Consumer loans | Home equity mortgages
Financing Receivable, Past Due [Line Items]
Nonaccrual Loans		7	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