LOANS - Consumer Loans Credit Scores (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	$ 702,056	$ 694,488
Unallocated portfolio layer cumulative basis adjustments		(72)
Consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	386,312	393,102
Unallocated portfolio layer cumulative basis adjustments	231	(224)
Consumer loans | In North America offices
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	313,086	321,948
Consumer loans | In North America offices | 90+ days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	2,982	3,162
Consumer loans | In North America offices | 90+ days past due | Banking
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	25,500	25,900
Consumer loans | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	72,995	71,378
Consumer loans | In offices outside North America | 90+ days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	320	310
Consumer loans | In offices outside North America | 90+ days past due | Banking
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	18,900	17,600
Consumer loans | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	311,840	320,631
Consumer loans | Residential mortgages | In North America offices
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	114,664	114,593
Consumer loans | Residential mortgages | In North America offices | 90+ days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	351	349
Consumer loans | Residential mortgages | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	24,326	24,456
Consumer loans | Residential mortgages | In offices outside North America | 90+ days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	60	60
Consumer loans | Residential mortgages | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	114,664	114,593
Consumer loans | Home equity loans | In North America offices
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	3,025	3,141
Consumer loans | Home equity loans | In North America offices | 90+ days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	53	58
Consumer loans | Home equity loans | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	3,025	3,141
Consumer loans | Credit cards | In North America offices
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	162,806	171,059
Consumer loans | Credit cards | In North America offices | 90+ days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	2,550	2,705
Consumer loans | Credit cards | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Revolving loans converted to term loans	34	33
Total loans, net of unearned income	12,885	12,927
Consumer loans | Credit cards | In offices outside North America | 90+ days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	223	214
Consumer loans | Credit cards | Canada
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	508	562
Consumer loans | Credit cards | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	162,298	170,497
Consumer loans | Personal, small business and other
Financing Receivable, Credit Quality Indicator [Line Items]
Revolving loans converted to term loans	20	22
Consumer loans | Personal, small business and other | In North America offices
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	32,591	33,155
Consumer loans | Personal, small business and other | In North America offices | 90+ days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	28	50
Consumer loans | Personal, small business and other | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	35,784	$ 33,995
Consumer loans | Personal, small business and other | In offices outside North America | Internal Investment Grade
Financing Receivable, Credit Quality Indicator [Line Items]
Percentage of loans rated investment grade		83.00%
Consumer loans | Personal, small business and other | In offices outside North America | 90+ days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	37	$ 36
Consumer loans | Personal, small business and other | Canada
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	738	755
Consumer loans | Personal, small business and other | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	31,853	32,400
Consumer loans | Classifiably Managed and Delinquency Managed | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	74,500	72,500
Consumer loans | Less than 660 | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	27,971	27,952
Consumer loans | Less than 660 | Residential mortgages | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	13	123
One year prior to current fiscal year	116	223
Two years prior to current fiscal year	211	354
Three years prior to current fiscal year	360	312
Four years prior to current fiscal year	342	298
Prior	1,738	1,473
Total loans, net of unearned income	2,780	2,783
Consumer loans | Less than 660 | Home equity line of credit (pre-reset) | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	259	266
Consumer loans | Less than 660 | Home equity line of credit (post-reset) | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	61	58
Consumer loans | Less than 660 | Home equity term loans | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
One year prior to current fiscal year	0	0
Two years prior to current fiscal year	0	0
Three years prior to current fiscal year	0	0
Four years prior to current fiscal year	0	0
Prior	45	45
Total loans, net of unearned income	45	45
Consumer loans | Less than 660 | Home equity loans | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	365	369
Consumer loans | Less than 660 | Credit cards | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	22,771	22,855
Consumer loans | Less than 660 | Credit cards | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Revolving loans converted to term loans	1,561	1,462
Total loans, net of unearned income	24,332	24,317
Consumer loans | Less than 660 | Personal, small business and other | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	5	96
One year prior to current fiscal year	132	132
Two years prior to current fiscal year	125	131
Three years prior to current fiscal year	114	28
Four years prior to current fiscal year	23	2
Prior	95	94
Total loans, net of unearned income	494	483
Consumer loans | 660 to 739 | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	77,351	79,930
Consumer loans | 660 to 739 | Residential mortgages | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	246	2,213
One year prior to current fiscal year	2,111	2,451
Two years prior to current fiscal year	2,311	3,272
Three years prior to current fiscal year	3,065	2,745
Four years prior to current fiscal year	2,601	1,990
Prior	6,677	5,034
Total loans, net of unearned income	17,011	17,705
Consumer loans | 660 to 739 | Home equity line of credit (pre-reset) | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	732	764
Consumer loans | 660 to 739 | Home equity line of credit (post-reset) | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	69	80
Consumer loans | 660 to 739 | Home equity term loans | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
One year prior to current fiscal year	0	0
Two years prior to current fiscal year	0	0
Three years prior to current fiscal year	0	0
Four years prior to current fiscal year	0	1
Prior	82	86
Total loans, net of unearned income	82	87
Consumer loans | 660 to 739 | Home equity loans | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	883	931
Consumer loans | 660 to 739 | Credit cards | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	57,691	59,574
Consumer loans | 660 to 739 | Credit cards | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Revolving loans converted to term loans	713	668
Total loans, net of unearned income	58,404	60,242
Consumer loans | 660 to 739 | Personal, small business and other | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	39	398
One year prior to current fiscal year	445	282
Two years prior to current fiscal year	246	180
Three years prior to current fiscal year	148	38
Four years prior to current fiscal year	30	2
Prior	145	152
Total loans, net of unearned income	1,053	1,052
Consumer loans | Greater than or equal to 740 | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	169,062	174,872
Consumer loans | Greater than or equal to 740 | Residential mortgages | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	1,724	10,308
One year prior to current fiscal year	10,224	12,936
Two years prior to current fiscal year	12,722	16,034
Three years prior to current fiscal year	15,959	14,651
Four years prior to current fiscal year	14,539	12,245
Prior	32,346	20,573
Total loans, net of unearned income	87,514	86,747
Consumer loans | Greater than or equal to 740 | Home equity line of credit (pre-reset) | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	1,539	1,597
Consumer loans | Greater than or equal to 740 | Home equity line of credit (post-reset) | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	78	75
Consumer loans | Greater than or equal to 740 | Home equity term loans | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
One year prior to current fiscal year	0	0
Two years prior to current fiscal year	0	0
Three years prior to current fiscal year	0	1
Four years prior to current fiscal year	1	2
Prior	107	111
Total loans, net of unearned income	108	114
Consumer loans | Greater than or equal to 740 | Home equity loans | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	1,725	1,786
Consumer loans | Greater than or equal to 740 | Credit cards | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	77,448	83,935
Consumer loans | Greater than or equal to 740 | Credit cards | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Revolving loans converted to term loans	135	129
Total loans, net of unearned income	77,583	84,064
Consumer loans | Greater than or equal to 740 | Personal, small business and other | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	163	1,219
One year prior to current fiscal year	1,215	577
Two years prior to current fiscal year	467	271
Three years prior to current fiscal year	216	54
Four years prior to current fiscal year	41	4
Prior	138	150
Total loans, net of unearned income	2,240	2,275
Consumer loans | Classifiably managed | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	18,937	17,553
Consumer loans | Classifiably managed | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	25,518	25,860
Consumer loans | Classifiably managed | Residential mortgages | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	0	0
Consumer loans | Classifiably managed | Residential mortgages | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	0	0
Consumer loans | Classifiably managed | Home equity loans | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	0	0
Consumer loans | Classifiably managed | Credit cards | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	0	0
Consumer loans | Classifiably managed | Credit cards | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	0	0
Consumer loans | Classifiably managed | Personal, small business and other | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	18,937	17,553
Consumer loans | Classifiably managed | Personal, small business and other | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	25,518	25,860
Consumer loans | FICO not available | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	11,938	12,017
Consumer loans | FICO not available | Residential mortgages | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	7,359	7,358
Consumer loans | FICO not available | Home equity loans | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	52	55
Consumer loans | FICO not available | Credit cards | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	1,979	1,874
Consumer loans | FICO not available | Personal, small business and other | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	$ 2,548	$ 2,730