Loans - Summary of Past Due Status of Loans (Detail) - USD ($) $ in Millions		Mar. 31, 2022	Dec. 31, 2021
Financing Receivable, Past Due [Line Items]
Loans	[1]	$ 58,610	$ 55,864
Commercial loans:
Financing Receivable, Past Due [Line Items]
Loans		42,454	39,796
Commercial loans: | Real Estate, including Construction
Financing Receivable, Past Due [Line Items]
Loans		8,020	8,234
Commercial loans: | Business and corporate banking
Financing Receivable, Past Due [Line Items]
Loans		15,305	13,958
Commercial loans: | Global banking
Financing Receivable, Past Due [Line Items]
Loans		11,948	11,109
Commercial loans: | Other commercial:
Financing Receivable, Past Due [Line Items]
Loans		7,181	6,495
Consumer loans:
Financing Receivable, Past Due [Line Items]
Loans		16,156	16,068
Consumer loans: | Residential mortgages
Financing Receivable, Past Due [Line Items]
Loans		15,573	15,469
Consumer loans: | Home equity mortgages
Financing Receivable, Past Due [Line Items]
Loans		306	325
Consumer loans: | Credit cards
Financing Receivable, Past Due [Line Items]
Loans		205	204
Consumer loans: | Other consumer
Financing Receivable, Past Due [Line Items]
Loans		72	70
Financial Asset, Past Due
Financing Receivable, Past Due [Line Items]
Loans		243	453
Financial Asset, Past Due | Commercial loans:
Financing Receivable, Past Due [Line Items]
Loans		88	241
Financial Asset, Past Due | Commercial loans: | Real Estate, including Construction
Financing Receivable, Past Due [Line Items]
Loans		8	38
Financial Asset, Past Due | Commercial loans: | Business and corporate banking
Financing Receivable, Past Due [Line Items]
Loans		60	129
Financial Asset, Past Due | Commercial loans: | Global banking
Financing Receivable, Past Due [Line Items]
Loans		12	27
Financial Asset, Past Due | Commercial loans: | Other commercial:
Financing Receivable, Past Due [Line Items]
Loans		8	47
Financial Asset, Past Due | Consumer loans:
Financing Receivable, Past Due [Line Items]
Loans		155	212
Financial Asset, Past Due | Consumer loans: | Residential mortgages
Financing Receivable, Past Due [Line Items]
Loans		150	201
Financial Asset, Past Due | Consumer loans: | Home equity mortgages
Financing Receivable, Past Due [Line Items]
Loans		2	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		0	1
30 - 89 Days
Financing Receivable, Past Due [Line Items]
Loans		192	343
30 - 89 Days | Commercial loans:
Financing Receivable, Past Due [Line Items]
Loans		59	197
30 - 89 Days | Commercial loans: | Real Estate, including Construction
Financing Receivable, Past Due [Line Items]
Loans		8	38
30 - 89 Days | Commercial loans: | Business and corporate banking
Financing Receivable, Past Due [Line Items]
Loans		43	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		8	47
30 - 89 Days | Consumer loans:
Financing Receivable, Past Due [Line Items]
Loans		133	146
30 - 89 Days | Consumer loans: | Residential mortgages
Financing Receivable, Past Due [Line Items]
Loans		130	138
30 - 89 Days | Consumer loans: | Home equity mortgages
Financing Receivable, Past Due [Line Items]
Loans		1	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		0	1
90+ Days
Financing Receivable, Past Due [Line Items]
Loans		51	110
90+ Days | Commercial loans:
Financing Receivable, Past Due [Line Items]
Loans		29	44
90+ Days | Commercial loans: | Real Estate, including Construction
Financing Receivable, Past Due [Line Items]
Loans		0	0
90+ Days | Commercial loans: | Business and corporate banking
Financing Receivable, Past Due [Line Items]
Loans		17	17
90+ Days | Commercial loans: | Global banking
Financing Receivable, Past Due [Line Items]
Loans		12	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		22	66
90+ Days | Consumer loans: | Residential mortgages
Financing Receivable, Past Due [Line Items]
Loans		20	63
90+ Days | Consumer loans: | Home equity mortgages
Financing Receivable, Past Due [Line Items]
Loans		1	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		58,367	55,411
Current | Commercial loans:
Financing Receivable, Past Due [Line Items]
Loans		42,366	39,555
Current | Commercial loans: | Real Estate, including Construction
Financing Receivable, Past Due [Line Items]
Loans		8,012	8,196
Current | Commercial loans: | Business and corporate banking
Financing Receivable, Past Due [Line Items]
Loans		15,245	13,829
Current | Commercial loans: | Global banking
Financing Receivable, Past Due [Line Items]
Loans		11,936	11,082
Current | Commercial loans: | Other commercial:
Financing Receivable, Past Due [Line Items]
Loans		7,173	6,448
Current | Consumer loans:
Financing Receivable, Past Due [Line Items]
Loans		16,001	15,856
Current | Consumer loans: | Residential mortgages
Financing Receivable, Past Due [Line Items]
Loans		15,423	15,268
Current | Consumer loans: | Home equity mortgages
Financing Receivable, Past Due [Line Items]
Loans		304	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		$ 72	$ 69

[1] The following table summarizes assets and liabilities related to our consolidated variable interest entities ("VIEs") at March 31, 2022 and December 31, 2021. Assets and liabilities exclude intercompany balances that eliminate in consolidation. See Note 17, "Variable Interest Entities," for additional information. March 31, 2022December 31, 2021(in millions)AssetsLoans$128 $46 Other assets51 55 Total assets$179 $101 LiabilitiesInterest, taxes and other liabilities$31 $9 Total liabilities$31 $9