Loans - Summary of Past Due Status of Loans (Detail) - USD ($) $ in Millions		3 Months Ended
		Jun. 30, 2022	Sep. 30, 2022	Dec. 31, 2021
Financing Receivable, Past Due [Line Items]
Loans	[1]		$ 61,775	$ 55,864
Commercial loans
Financing Receivable, Past Due [Line Items]
Loans			44,467	39,796
Commercial loans | Real estate, including construction
Financing Receivable, Past Due [Line Items]
Loans			8,395	8,234
Commercial loans | Business and corporate banking
Financing Receivable, Past Due [Line Items]
Loans			16,730	13,958
Commercial loans | Global banking
Financing Receivable, Past Due [Line Items]
Loans			12,142	11,109
Commercial loans | Other commercial
Financing Receivable, Past Due [Line Items]
Loans			7,200	6,495
Consumer loans
Financing Receivable, Past Due [Line Items]
Loans			17,308	16,068
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]
Loans			16,691	15,469
Consumer loans | Home equity mortgages
Financing Receivable, Past Due [Line Items]
Loans			345	325
Consumer loans | Credit cards
Financing Receivable, Past Due [Line Items]
Loans			198	204
Consumer loans | Other consumer
Financing Receivable, Past Due [Line Items]
Loans			74	70
Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans			508	453
Financial Asset, Past Due | Commercial loans
Financing Receivable, Past Due [Line Items]
Loans			226	241
Financial Asset, Past Due | Commercial loans | Real estate, including construction
Financing Receivable, Past Due [Line Items]
Loans			93	38
Financial Asset, Past Due | Commercial loans | Business and corporate banking
Financing Receivable, Past Due [Line Items]
Loans			96	129
Financial Asset, Past Due | Commercial loans | Global banking
Financing Receivable, Past Due [Line Items]
Loans			28	27
Financial Asset, Past Due | Commercial loans | Other commercial
Financing Receivable, Past Due [Line Items]
Loans			9	47
Financial Asset, Past Due | Consumer loans
Financing Receivable, Past Due [Line Items]
Loans			282	212
Transfer of loans held-for-sale to held-for-investment		$ 50
Financial Asset, Past Due | Consumer loans | Residential mortgages
Financing Receivable, Past Due [Line Items]
Loans			271	201
Financial Asset, Past Due | Consumer loans | Home equity mortgages
Financing Receivable, Past Due [Line Items]
Loans			7	3
Financial Asset, Past Due | Consumer loans | Credit cards
Financing Receivable, Past Due [Line Items]
Loans			3	7
Financial Asset, Past Due | Consumer loans | Other consumer
Financing Receivable, Past Due [Line Items]
Loans			1	1
30 - 89 Days
Financing Receivable, Past Due [Line Items]
Loans			289	343
30 - 89 Days | Commercial loans
Financing Receivable, Past Due [Line Items]
Loans			106	197
30 - 89 Days | Commercial loans | Real estate, including construction
Financing Receivable, Past Due [Line Items]
Loans			1	38
30 - 89 Days | Commercial loans | Business and corporate banking
Financing Receivable, Past Due [Line Items]
Loans			74	112
30 - 89 Days | Commercial loans | Global banking
Financing Receivable, Past Due [Line Items]
Loans			25	0
30 - 89 Days | Commercial loans | Other commercial
Financing Receivable, Past Due [Line Items]
Loans			6	47
30 - 89 Days | Consumer loans
Financing Receivable, Past Due [Line Items]
Loans			183	146
30 - 89 Days | Consumer loans | Residential mortgages
Financing Receivable, Past Due [Line Items]
Loans			176	138
30 - 89 Days | Consumer loans | Home equity mortgages
Financing Receivable, Past Due [Line Items]
Loans			4	2
30 - 89 Days | Consumer loans | Credit cards
Financing Receivable, Past Due [Line Items]
Loans			2	5
30 - 89 Days | Consumer loans | Other consumer
Financing Receivable, Past Due [Line Items]
Loans			1	1
90+ Days
Financing Receivable, Past Due [Line Items]
Loans			219	110
90+ Days | Commercial loans
Financing Receivable, Past Due [Line Items]
Loans			120	44
90+ Days | Commercial loans | Real estate, including construction
Financing Receivable, Past Due [Line Items]
Loans			92	0
90+ Days | Commercial loans | Business and corporate banking
Financing Receivable, Past Due [Line Items]
Loans			22	17
90+ Days | Commercial loans | Global banking
Financing Receivable, Past Due [Line Items]
Loans			3	27
90+ Days | Commercial loans | Other commercial
Financing Receivable, Past Due [Line Items]
Loans			3	0
90+ Days | Consumer loans
Financing Receivable, Past Due [Line Items]
Loans			99	66
90+ Days | Consumer loans | Residential mortgages
Financing Receivable, Past Due [Line Items]
Loans			95	63
90+ Days | Consumer loans | Home equity mortgages
Financing Receivable, Past Due [Line Items]
Loans			3	1
90+ Days | Consumer loans | Credit cards
Financing Receivable, Past Due [Line Items]
Loans			1	2
90+ Days | Consumer loans | Other consumer
Financing Receivable, Past Due [Line Items]
Loans			0	0
Current
Financing Receivable, Past Due [Line Items]
Loans			61,267	55,411
Current | Commercial loans
Financing Receivable, Past Due [Line Items]
Loans			44,241	39,555
Current | Commercial loans | Real estate, including construction
Financing Receivable, Past Due [Line Items]
Loans			8,302	8,196
Current | Commercial loans | Business and corporate banking
Financing Receivable, Past Due [Line Items]
Loans			16,634	13,829
Current | Commercial loans | Global banking
Financing Receivable, Past Due [Line Items]
Loans			12,114	11,082
Current | Commercial loans | Other commercial
Financing Receivable, Past Due [Line Items]
Loans			7,191	6,448
Current | Consumer loans
Financing Receivable, Past Due [Line Items]
Loans			17,026	15,856
Current | Consumer loans | Residential mortgages
Financing Receivable, Past Due [Line Items]
Loans			16,420	15,268
Current | Consumer loans | Home equity mortgages
Financing Receivable, Past Due [Line Items]
Loans			338	322
Current | Consumer loans | Credit cards
Financing Receivable, Past Due [Line Items]
Loans			195	197
Current | Consumer loans | Other consumer
Financing Receivable, Past Due [Line Items]
Loans			$ 73	$ 69

[1] The following table summarizes assets and liabilities related to our consolidated variable interest entities ("VIEs") at September 30, 2022 and December 31, 2021. Assets and liabilities exclude intercompany balances that eliminate in consolidation. See Note 17, "Variable Interest Entities," for additional information. September 30, 2022December 31, 2021(in millions)AssetsLoans$127 $46 Other assets44 55 Total assets$171 $101 LiabilitiesInterest, taxes and other liabilities$26 $9 Total liabilities$26 $9