Loans - Summary of Past Due Status of Loans (Detail) - USD ($) $ in Millions		Dec. 31, 2024	Dec. 31, 2023
Financing Receivable, Past Due [Line Items]
Loans, net	[1]	$ 62,753	$ 58,987
Commercial loans
Financing Receivable, Past Due [Line Items]
Loans, net		41,051	39,957
Commercial loans | Real estate, including construction
Financing Receivable, Past Due [Line Items]
Loans, net		6,612	7,087
Commercial loans | Business and corporate banking
Financing Receivable, Past Due [Line Items]
Loans, net		15,431	15,724
Commercial loans | Global banking
Financing Receivable, Past Due [Line Items]
Loans, net		9,995	10,725
Commercial loans | Other commercial
Financing Receivable, Past Due [Line Items]
Loans, net		9,013	6,421
Consumer loans
Financing Receivable, Past Due [Line Items]
Loans, net		21,702	19,030
Consumer loans | Residential mortgages
Financing Receivable, Past Due [Line Items]
Loans, net		21,035	18,341
Consumer loans | Home equity mortgages
Financing Receivable, Past Due [Line Items]
Loans, net		393	389
Consumer loans | Credit cards
Financing Receivable, Past Due [Line Items]
Loans, net		195	199
Consumer loans | Other consumer
Financing Receivable, Past Due [Line Items]
Loans, net		79	101
Total Past Due 30 Days or More
Financing Receivable, Past Due [Line Items]
Loans, net		591	852
Total Past Due 30 Days or More | Commercial loans
Financing Receivable, Past Due [Line Items]
Loans, net		299	561
Total Past Due 30 Days or More | Commercial loans | Real estate, including construction
Financing Receivable, Past Due [Line Items]
Loans, net		23	206
Total Past Due 30 Days or More | Commercial loans | Business and corporate banking
Financing Receivable, Past Due [Line Items]
Loans, net		155	4
Total Past Due 30 Days or More | Commercial loans | Global banking
Financing Receivable, Past Due [Line Items]
Loans, net		90	1
Total Past Due 30 Days or More | Commercial loans | Other commercial
Financing Receivable, Past Due [Line Items]
Loans, net		31	350
Total Past Due 30 Days or More | Consumer loans
Financing Receivable, Past Due [Line Items]
Loans, net		292	291
Total Past Due 30 Days or More | Consumer loans | Residential mortgages
Financing Receivable, Past Due [Line Items]
Loans, net		279	265
Total Past Due 30 Days or More | Consumer loans | Home equity mortgages
Financing Receivable, Past Due [Line Items]
Loans, net		6	15
Total Past Due 30 Days or More | Consumer loans | Credit cards
Financing Receivable, Past Due [Line Items]
Loans, net		4	6
Total Past Due 30 Days or More | Consumer loans | Other consumer
Financing Receivable, Past Due [Line Items]
Loans, net		3	5
30 - 89 Days
Financing Receivable, Past Due [Line Items]
Loans, net		278	543
30 - 89 Days | Commercial loans
Financing Receivable, Past Due [Line Items]
Loans, net		98	351
30 - 89 Days | Commercial loans | Real estate, including construction
Financing Receivable, Past Due [Line Items]
Loans, net		4	0
30 - 89 Days | Commercial loans | Business and corporate banking
Financing Receivable, Past Due [Line Items]
Loans, net		59	1
30 - 89 Days | Commercial loans | Global banking
Financing Receivable, Past Due [Line Items]
Loans, net		4	0
30 - 89 Days | Commercial loans | Other commercial
Financing Receivable, Past Due [Line Items]
Loans, net		31	350
30 - 89 Days | Consumer loans
Financing Receivable, Past Due [Line Items]
Loans, net		180	192
30 - 89 Days | Consumer loans | Residential mortgages
Financing Receivable, Past Due [Line Items]
Loans, net		174	174
30 - 89 Days | Consumer loans | Home equity mortgages
Financing Receivable, Past Due [Line Items]
Loans, net		2	12
30 - 89 Days | Consumer loans | Credit cards
Financing Receivable, Past Due [Line Items]
Loans, net		2	3
30 - 89 Days | Consumer loans | Other consumer
Financing Receivable, Past Due [Line Items]
Loans, net		2	3
90+ Days
Financing Receivable, Past Due [Line Items]
Loans, net		313	309
90+ Days | Commercial loans
Financing Receivable, Past Due [Line Items]
Loans, net		201	210
90+ Days | Commercial loans | Real estate, including construction
Financing Receivable, Past Due [Line Items]
Loans, net		19	206
90+ Days | Commercial loans | Business and corporate banking
Financing Receivable, Past Due [Line Items]
Loans, net		96	3
90+ Days | Commercial loans | Global banking
Financing Receivable, Past Due [Line Items]
Loans, net		86	1
90+ Days | Commercial loans | Other commercial
Financing Receivable, Past Due [Line Items]
Loans, net		0	0
90+ Days | Consumer loans
Financing Receivable, Past Due [Line Items]
Loans, net		112	99
90+ Days | Consumer loans | Residential mortgages
Financing Receivable, Past Due [Line Items]
Loans, net		105	91
90+ Days | Consumer loans | Home equity mortgages
Financing Receivable, Past Due [Line Items]
Loans, net		4	3
90+ Days | Consumer loans | Credit cards
Financing Receivable, Past Due [Line Items]
Loans, net		2	3
90+ Days | Consumer loans | Other consumer
Financing Receivable, Past Due [Line Items]
Loans, net		1	2
Current
Financing Receivable, Past Due [Line Items]
Loans, net		62,162	58,135
Current | Commercial loans
Financing Receivable, Past Due [Line Items]
Loans, net		40,752	39,396
Current | Commercial loans | Real estate, including construction
Financing Receivable, Past Due [Line Items]
Loans, net		6,589	6,881
Current | Commercial loans | Business and corporate banking
Financing Receivable, Past Due [Line Items]
Loans, net		15,276	15,720
Current | Commercial loans | Global banking
Financing Receivable, Past Due [Line Items]
Loans, net		9,905	10,724
Current | Commercial loans | Other commercial
Financing Receivable, Past Due [Line Items]
Loans, net		8,982	6,071
Current | Consumer loans
Financing Receivable, Past Due [Line Items]
Loans, net		21,410	18,739
Current | Consumer loans | Residential mortgages
Financing Receivable, Past Due [Line Items]
Loans, net		20,756	18,076
Current | Consumer loans | Home equity mortgages
Financing Receivable, Past Due [Line Items]
Loans, net		387	374
Current | Consumer loans | Credit cards
Financing Receivable, Past Due [Line Items]
Loans, net		191	193
Current | Consumer loans | Other consumer
Financing Receivable, Past Due [Line Items]
Loans, net		$ 76	$ 96

[1] The following table summarizes assets and liabilities related to our consolidated variable interest entities ("VIEs") at December 31, 2024 and 2023. Assets and liabilities exclude intercompany balances that eliminate in consolidation. See Note 27, "Variable Interest Entities," for additional information. At December 31,20242023(in millions)AssetsOther assets$11 $23 Total assets$11 $23 LiabilitiesInterest, taxes and other liabilities$4 $17 Total liabilities$4 $17