Loans - Summary of Past Due Status of Loans (Detail) - USD ($) $ in Millions		Dec. 31, 2023	Dec. 31, 2022
Financing Receivable, Past Due [Line Items]
Loans, net	[1]	$ 58,987	$ 59,380
Commercial loans
Financing Receivable, Past Due [Line Items]
Loans, net		39,957	41,817
Commercial loans | Real estate, including construction
Financing Receivable, Past Due [Line Items]
Loans, net		7,087	7,963
Commercial loans | Business and corporate banking
Financing Receivable, Past Due [Line Items]
Loans, net		15,724	16,075
Commercial loans | Global banking
Financing Receivable, Past Due [Line Items]
Loans, net		10,725	10,578
Commercial loans | Other commercial
Financing Receivable, Past Due [Line Items]
Loans, net		6,421	7,201
Consumer loans
Financing Receivable, Past Due [Line Items]
Loans, net		19,030	17,563
Consumer loans | Residential mortgages
Financing Receivable, Past Due [Line Items]
Loans, net		18,341	16,838
Consumer loans | Home equity mortgages
Financing Receivable, Past Due [Line Items]
Loans, net		389	370
Consumer loans | Credit cards
Financing Receivable, Past Due [Line Items]
Loans, net		199	213
Consumer loans | Other consumer
Financing Receivable, Past Due [Line Items]
Loans, net		101	142
Past Due
Financing Receivable, Past Due [Line Items]
Loans, net		852	833
Past Due | Commercial loans
Financing Receivable, Past Due [Line Items]
Loans, net		561	536
Past Due | Commercial loans | Real estate, including construction
Financing Receivable, Past Due [Line Items]
Loans, net		206	28
Past Due | Commercial loans | Business and corporate banking
Financing Receivable, Past Due [Line Items]
Loans, net		4	36
Past Due | Commercial loans | Global banking
Financing Receivable, Past Due [Line Items]
Loans, net		1	8
Past Due | Commercial loans | Other commercial
Financing Receivable, Past Due [Line Items]
Loans, net		350	464
Past Due | Consumer loans
Financing Receivable, Past Due [Line Items]
Loans, net		291	297
Past Due | Consumer loans | Residential mortgages
Financing Receivable, Past Due [Line Items]
Loans, net		265	285
Past Due | Consumer loans | Home equity mortgages
Financing Receivable, Past Due [Line Items]
Loans, net		15	5
Past Due | Consumer loans | Credit cards
Financing Receivable, Past Due [Line Items]
Loans, net		6	4
Past Due | Consumer loans | Other consumer
Financing Receivable, Past Due [Line Items]
Loans, net		5	3
30 - 89 Days
Financing Receivable, Past Due [Line Items]
Loans, net		543	690
30 - 89 Days | Commercial loans
Financing Receivable, Past Due [Line Items]
Loans, net		351	504
30 - 89 Days | Commercial loans | Real estate, including construction
Financing Receivable, Past Due [Line Items]
Loans, net		0	27
30 - 89 Days | Commercial loans | Business and corporate banking
Financing Receivable, Past Due [Line Items]
Loans, net		1	13
30 - 89 Days | Commercial loans | Global banking
Financing Receivable, Past Due [Line Items]
Loans, net		0	0
30 - 89 Days | Commercial loans | Other commercial
Financing Receivable, Past Due [Line Items]
Loans, net		350	464
30 - 89 Days | Consumer loans
Financing Receivable, Past Due [Line Items]
Loans, net		192	186
30 - 89 Days | Consumer loans | Residential mortgages
Financing Receivable, Past Due [Line Items]
Loans, net		174	180
30 - 89 Days | Consumer loans | Home equity mortgages
Financing Receivable, Past Due [Line Items]
Loans, net		12	2
30 - 89 Days | Consumer loans | Credit cards
Financing Receivable, Past Due [Line Items]
Loans, net		3	2
30 - 89 Days | Consumer loans | Other consumer
Financing Receivable, Past Due [Line Items]
Loans, net		3	2
90+ Days
Financing Receivable, Past Due [Line Items]
Loans, net		309	143
90+ Days | Commercial loans
Financing Receivable, Past Due [Line Items]
Loans, net		210	32
90+ Days | Commercial loans | Real estate, including construction
Financing Receivable, Past Due [Line Items]
Loans, net		206	1
90+ Days | Commercial loans | Business and corporate banking
Financing Receivable, Past Due [Line Items]
Loans, net		3	23
90+ Days | Commercial loans | Global banking
Financing Receivable, Past Due [Line Items]
Loans, net		1	8
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		99	111
90+ Days | Consumer loans | Residential mortgages
Financing Receivable, Past Due [Line Items]
Loans, net		91	105
90+ Days | Consumer loans | Home equity mortgages
Financing Receivable, Past Due [Line Items]
Loans, net		3	3
90+ Days | Consumer loans | Credit cards
Financing Receivable, Past Due [Line Items]
Loans, net		3	2
90+ Days | Consumer loans | Other consumer
Financing Receivable, Past Due [Line Items]
Loans, net		2	1
Current
Financing Receivable, Past Due [Line Items]
Loans, net		58,135	58,547
Current | Commercial loans
Financing Receivable, Past Due [Line Items]
Loans, net		39,396	41,281
Current | Commercial loans | Real estate, including construction
Financing Receivable, Past Due [Line Items]
Loans, net		6,881	7,935
Current | Commercial loans | Business and corporate banking
Financing Receivable, Past Due [Line Items]
Loans, net		15,720	16,039
Current | Commercial loans | Global banking
Financing Receivable, Past Due [Line Items]
Loans, net		10,724	10,570
Current | Commercial loans | Other commercial
Financing Receivable, Past Due [Line Items]
Loans, net		6,071	6,737
Current | Consumer loans
Financing Receivable, Past Due [Line Items]
Loans, net		18,739	17,266
Current | Consumer loans | Residential mortgages
Financing Receivable, Past Due [Line Items]
Loans, net		18,076	16,553
Current | Consumer loans | Home equity mortgages
Financing Receivable, Past Due [Line Items]
Loans, net		374	365
Current | Consumer loans | Credit cards
Financing Receivable, Past Due [Line Items]
Loans, net		193	209
Current | Consumer loans | Other consumer
Financing Receivable, Past Due [Line Items]
Loans, net		$ 96	$ 139

[1] The following table summarizes assets and liabilities related to our consolidated variable interest entities ("VIEs") at December 31, 2023 and 2022. Assets and liabilities exclude intercompany balances that eliminate in consolidation. See Note 27, "Variable Interest Entities," for additional information. At December 31,20232022(in millions)AssetsLoans, net$— $162 Other assets23 44 Total assets$23 $206 LiabilitiesInterest, taxes and other liabilities$17 $22 Total liabilities$17 $22