Loans - Summary of Past Due Status of Loans (Detail) - USD ($) $ in Millions		3 Months Ended
		Jun. 30, 2022	Dec. 31, 2021
Financing Receivable, Past Due [Line Items]
Loans	[1]	$ 61,798	$ 55,864
Commercial loans
Financing Receivable, Past Due [Line Items]
Loans		44,695	39,796
Commercial loans | Real estate, including construction
Financing Receivable, Past Due [Line Items]
Loans		8,791	8,234
Commercial loans | Business and corporate banking
Financing Receivable, Past Due [Line Items]
Loans		16,108	13,958
Commercial loans | Global banking
Financing Receivable, Past Due [Line Items]
Loans		12,963	11,109
Commercial loans | Other commercial
Financing Receivable, Past Due [Line Items]
Loans		6,833	6,495
Consumer loans
Financing Receivable, Past Due [Line Items]
Loans		17,103	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		16,475	15,469
Consumer loans | Home equity mortgages
Financing Receivable, Past Due [Line Items]
Loans		351	325
Consumer loans | Credit cards
Financing Receivable, Past Due [Line Items]
Loans		204	204
Consumer loans | Other consumer
Financing Receivable, Past Due [Line Items]
Loans		73	70
Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans		783	453
Financial Asset, Past Due | Commercial loans
Financing Receivable, Past Due [Line Items]
Loans		539	241
Financial Asset, Past Due | Commercial loans | Real estate, including construction
Financing Receivable, Past Due [Line Items]
Loans		109	38
Financial Asset, Past Due | Commercial loans | Business and corporate banking
Financing Receivable, Past Due [Line Items]
Loans		76	129
Financial Asset, Past Due | Commercial loans | Global banking
Financing Receivable, Past Due [Line Items]
Loans		3	27
Financial Asset, Past Due | Commercial loans | Other commercial
Financing Receivable, Past Due [Line Items]
Loans		351	47
Financial Asset, Past Due | Consumer loans
Financing Receivable, Past Due [Line Items]
Loans		244	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		237	201
Financial Asset, Past Due | Consumer loans | Home equity mortgages
Financing Receivable, Past Due [Line Items]
Loans		5	3
Financial Asset, Past Due | Consumer loans | Credit cards
Financing Receivable, Past Due [Line Items]
Loans		2	7
Financial Asset, Past Due | Consumer loans | Other consumer
Financing Receivable, Past Due [Line Items]
Loans		0	1
30 - 89 Days
Financing Receivable, Past Due [Line Items]
Loans		598	343
30 - 89 Days | Commercial loans
Financing Receivable, Past Due [Line Items]
Loans		444	197
30 - 89 Days | Commercial loans | Real estate, including construction
Financing Receivable, Past Due [Line Items]
Loans		33	38
30 - 89 Days | Commercial loans | Business and corporate banking
Financing Receivable, Past Due [Line Items]
Loans		60	112
30 - 89 Days | Commercial loans | Global banking
Financing Receivable, Past Due [Line Items]
Loans		0	0
30 - 89 Days | Commercial loans | Other commercial
Financing Receivable, Past Due [Line Items]
Loans		351	47
30 - 89 Days | Consumer loans
Financing Receivable, Past Due [Line Items]
Loans		154	146
30 - 89 Days | Consumer loans | Residential mortgages
Financing Receivable, Past Due [Line Items]
Loans		151	138
30 - 89 Days | Consumer loans | Home equity mortgages
Financing Receivable, Past Due [Line Items]
Loans		2	2
30 - 89 Days | Consumer loans | Credit cards
Financing Receivable, Past Due [Line Items]
Loans		1	5
30 - 89 Days | Consumer loans | Other consumer
Financing Receivable, Past Due [Line Items]
Loans		0	1
90+ Days
Financing Receivable, Past Due [Line Items]
Loans		185	110
90+ Days | Commercial loans
Financing Receivable, Past Due [Line Items]
Loans		95	44
90+ Days | Commercial loans | Real estate, including construction
Financing Receivable, Past Due [Line Items]
Loans		76	0
90+ Days | Commercial loans | Business and corporate banking
Financing Receivable, Past Due [Line Items]
Loans		16	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		0	0
90+ Days | Consumer loans
Financing Receivable, Past Due [Line Items]
Loans		90	66
90+ Days | Consumer loans | Residential mortgages
Financing Receivable, Past Due [Line Items]
Loans		86	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		61,015	55,411
Current | Commercial loans
Financing Receivable, Past Due [Line Items]
Loans		44,156	39,555
Current | Commercial loans | Real estate, including construction
Financing Receivable, Past Due [Line Items]
Loans		8,682	8,196
Current | Commercial loans | Business and corporate banking
Financing Receivable, Past Due [Line Items]
Loans		16,032	13,829
Current | Commercial loans | Global banking
Financing Receivable, Past Due [Line Items]
Loans		12,960	11,082
Current | Commercial loans | Other commercial
Financing Receivable, Past Due [Line Items]
Loans		6,482	6,448
Current | Consumer loans
Financing Receivable, Past Due [Line Items]
Loans		16,859	15,856
Current | Consumer loans | Residential mortgages
Financing Receivable, Past Due [Line Items]
Loans		16,238	15,268
Current | Consumer loans | Home equity mortgages
Financing Receivable, Past Due [Line Items]
Loans		346	322
Current | Consumer loans | Credit cards
Financing Receivable, Past Due [Line Items]
Loans		202	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 June 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. June 30, 2022December 31, 2021(in millions)AssetsLoans$118 $46 Other assets46 55 Total assets$164 $101 LiabilitiesInterest, taxes and other liabilities$28 $9 Total liabilities$28 $9