Loans - Credit Risk Profile of Commercial Loans (Detail) - USD ($) $ in Millions		Dec. 31, 2024	Dec. 31, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Total	[1]	$ 62,753	$ 58,987
Commercial loans
Financing Receivable, Credit Quality Indicator [Line Items]
Current year		3,852	4,656
One year prior to current year		3,821	3,868
Two years prior to current year		3,112	3,250
Three years prior to current year		3,004	1,388
Four years prior to current year		1,042	2,354
Prior		11,633	11,069
Revolving Loans		14,289	13,054
Revolving Loans Converted to Term Loans		298	318
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Total		41,051	39,957
Commercial loans | Real estate, including construction
Financing Receivable, Credit Quality Indicator [Line Items]
Current year		1,035	920
One year prior to current year		946	1,286
Two years prior to current year		1,109	1,019
Three years prior to current year		882	355
Four years prior to current year		262	1,054
Prior		2,339	2,409
Revolving Loans		36	41
Revolving Loans Converted to Term Loans		3	3
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Total		6,612	7,087
Commercial loans | Business and corporate banking
Financing Receivable, Credit Quality Indicator [Line Items]
Current year		1,240	1,270
One year prior to current year		1,395	1,148
Two years prior to current year		978	1,074
Three years prior to current year		1,251	231
Four years prior to current year		155	561
Prior		3,770	4,253
Revolving Loans		6,347	6,922
Revolving Loans Converted to Term Loans		295	265
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Total		15,431	15,724
Commercial loans | Global banking
Financing Receivable, Credit Quality Indicator [Line Items]
Current year		1,084	2,255
One year prior to current year		1,390	1,153
Two years prior to current year		744	844
Three years prior to current year		735	151
Four years prior to current year		121	321
Prior		3,959	3,600
Revolving Loans		1,962	2,351
Revolving Loans Converted to Term Loans		0	50
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Total		9,995	10,725
Commercial loans | Other commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Current year		493	211
One year prior to current year		90	281
Two years prior to current year		281	313
Three years prior to current year		136	651
Four years prior to current year		504	418
Prior		1,565	807
Revolving Loans		5,944	3,740
Revolving Loans Converted to Term Loans		0	0
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Total		9,013	6,421
Commercial loans | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Current year		1,757	3,217
One year prior to current year		2,046	1,705
Two years prior to current year		1,149	1,261
Three years prior to current year		1,443	807
Four years prior to current year		575	1,028
Prior		6,911	6,322
Revolving Loans		10,535	8,595
Revolving Loans Converted to Term Loans		88	54
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Total		24,504	22,989
Commercial loans | Investment grade | Real estate, including construction
Financing Receivable, Credit Quality Indicator [Line Items]
Current year		67	327
One year prior to current year		307	100
Two years prior to current year		27	24
Three years prior to current year		0	187
Four years prior to current year		165	162
Prior		757	939
Revolving Loans		0	1
Revolving Loans Converted to Term Loans		0	0
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Total		1,323	1,740
Commercial loans | Investment grade | Business and corporate banking
Financing Receivable, Credit Quality Indicator [Line Items]
Current year		401	732
One year prior to current year		563	304
Two years prior to current year		310	543
Three years prior to current year		723	95
Four years prior to current year		86	261
Prior		1,626	1,977
Revolving Loans		3,084	3,311
Revolving Loans Converted to Term Loans		88	54
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Total		6,881	7,277
Commercial loans | Investment grade | Global banking
Financing Receivable, Credit Quality Indicator [Line Items]
Current year		924	1,947
One year prior to current year		1,105	1,109
Two years prior to current year		671	651
Three years prior to current year		634	149
Four years prior to current year		104	307
Prior		3,270	2,842
Revolving Loans		1,668	2,140
Revolving Loans Converted to Term Loans		0	0
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Total		8,376	9,145
Commercial loans | Investment grade | Other commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Current year		365	211
One year prior to current year		71	192
Two years prior to current year		141	43
Three years prior to current year		86	376
Four years prior to current year		220	298
Prior		1,258	564
Revolving Loans		5,783	3,143
Revolving Loans Converted to Term Loans		0	0
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Total		7,924	4,827
Commercial loans | Non-investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Current year		2,095	1,439
One year prior to current year		1,775	2,163
Two years prior to current year		1,963	1,989
Three years prior to current year		1,561	581
Four years prior to current year		467	1,326
Prior		4,722	4,747
Revolving Loans		3,754	4,459
Revolving Loans Converted to Term Loans		210	264
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Total		16,547	16,968
Commercial loans | Non-investment grade | Real estate, including construction
Financing Receivable, Credit Quality Indicator [Line Items]
Current year		968	593
One year prior to current year		639	1,186
Two years prior to current year		1,082	995
Three years prior to current year		882	168
Four years prior to current year		97	892
Prior		1,582	1,470
Revolving Loans		36	40
Revolving Loans Converted to Term Loans		3	3
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Total		5,289	5,347
Commercial loans | Non-investment grade | Business and corporate banking
Financing Receivable, Credit Quality Indicator [Line Items]
Current year		839	538
One year prior to current year		832	844
Two years prior to current year		668	531
Three years prior to current year		528	136
Four years prior to current year		69	300
Prior		2,144	2,276
Revolving Loans		3,263	3,611
Revolving Loans Converted to Term Loans		207	211
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Total		8,550	8,447
Commercial loans | Non-investment grade | Global banking
Financing Receivable, Credit Quality Indicator [Line Items]
Current year		160	308
One year prior to current year		285	44
Two years prior to current year		73	193
Three years prior to current year		101	2
Four years prior to current year		17	14
Prior		689	758
Revolving Loans		294	211
Revolving Loans Converted to Term Loans		0	50
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Total		1,619	1,580
Commercial loans | Non-investment grade | Other commercial
Financing Receivable, Credit Quality Indicator [Line Items]
Current year		128	0
One year prior to current year		19	89
Two years prior to current year		140	270
Three years prior to current year		50	275
Four years prior to current year		284	120
Prior		307	243
Revolving Loans		161	597
Revolving Loans Converted to Term Loans		0	0
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Total		$ 1,089	$ 1,594

[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