LOANS - Consumer Loans Credit Scores (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	$ 674,578	$ 689,362
Unallocated portfolio layer cumulative basis adjustments	(113)	93
Consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	381,759	389,197
Unallocated portfolio layer cumulative basis adjustments	(74)
Consumer loans | 90+ days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income		3,233
Consumer loans | In North America offices
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	306,803	313,158
Consumer loans | In North America offices | 90+ days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	2,986	2,897
Consumer loans | In North America offices | 90+ days past due | Personal Banking and Wealth Management [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	27,100	29,200
Consumer loans | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	75,030	76,039
Consumer loans | In offices outside North America | 90+ days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	324	336
Consumer loans | In offices outside North America | 90+ days past due | Personal Banking and Wealth Management [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	17,100	17,000
Consumer loans | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	110,592	108,711
Consumer loans | Residential mortgages | In North America offices
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	110,592	108,711
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	286	294
Consumer loans | Residential mortgages | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	25,926	26,426
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	72	69
Consumer loans | Home equity loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	3,439	3,592
Consumer loans | Home equity loans | In North America offices
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	3,439	3,592
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	83	85
Consumer loans | Credit cards
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	158,238	164,110
Consumer loans | Credit cards | In North America offices
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	158,806	164,720
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	2,563	2,461
Consumer loans | Credit cards | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Revolving loans converted to term loans	34	51
Total loans, net of unearned income	13,942	14,233
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	215	227
Consumer loans | Credit cards | Canada
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	568	610
Consumer loans | Personal, small business and other
Financing Receivable, Credit Quality Indicator [Line Items]
Revolving loans converted to term loans	32	37
Total loans, net of unearned income	33,095	35,258
Consumer loans | Personal, small business and other | In North America offices
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	33,966	36,135
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	54	57
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	35,162	$ 35,380
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		92.00%
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	$ 40
Consumer loans | Personal, small business and other | Canada
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	871	877
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	76,500	77,500
Consumer loans | Less than 660
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	26,839	26,297
Consumer loans | Less than 660 | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	20	163
One year prior to current fiscal year	208	339
Two years prior to current fiscal year	415	270
Three years prior to current fiscal year	341	232
Four years prior to current fiscal year	236	138
Prior	1,556	1,377
Total loans, net of unearned income	2,776	2,519
Consumer loans | Less than 660 | Home equity line of credit (pre-reset)
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	309	300
Consumer loans | Less than 660 | Home equity line of credit (post-reset)
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	67	61
Consumer loans | Less than 660 | Home equity term loans
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	2
Four years prior to current fiscal year	0	0
Prior	55	54
Total loans, net of unearned income	55	56
Consumer loans | Less than 660 | Home equity loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	431	417
Consumer loans | Less than 660 | Credit cards
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	22,007	21,899
Consumer loans | Less than 660 | Credit cards
Financing Receivable, Credit Quality Indicator [Line Items]
Revolving loans converted to term loans	1,156	1,011
Total loans, net of unearned income	23,163	22,910
Consumer loans | Less than 660 | Personal, small business and other
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	5	88
One year prior to current fiscal year	122	204
Two years prior to current fiscal year	190	52
Three years prior to current fiscal year	47	6
Four years prior to current fiscal year	5	5
Prior	100	96
Total loans, net of unearned income	469	451
Consumer loans | 660 to 739
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	76,270	76,958
Consumer loans | 660 to 739 | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	402	2,758
One year prior to current fiscal year	2,980	3,423
Two years prior to current fiscal year	3,291	3,107
Three years prior to current fiscal year	2,939	2,143
Four years prior to current fiscal year	2,293	1,382
Prior	5,281	4,122
Total loans, net of unearned income	17,186	16,935
Consumer loans | 660 to 739 | Home equity line of credit (pre-reset)
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	862	905
Consumer loans | 660 to 739 | Home equity line of credit (post-reset)
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	71	76
Consumer loans | 660 to 739 | Home equity term loans
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	1
Prior	102	109
Total loans, net of unearned income	103	111
Consumer loans | 660 to 739 | Home equity loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	1,036	1,092
Consumer loans | 660 to 739 | Credit cards
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	56,522	57,479
Consumer loans | 660 to 739 | Credit cards
Financing Receivable, Credit Quality Indicator [Line Items]
Revolving loans converted to term loans	534	490
Total loans, net of unearned income	57,056	57,969
Consumer loans | 660 to 739 | Personal, small business and other
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	41	343
One year prior to current fiscal year	404	351
Two years prior to current fiscal year	305	83
Three years prior to current fiscal year	71	9
Four years prior to current fiscal year	7	7
Prior	164	169
Total loans, net of unearned income	992	962
Consumer loans | Greater than or equal to 740
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	162,775	166,745
Consumer loans | Greater than or equal to 740 | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	2,508	14,309
One year prior to current fiscal year	13,956	16,834
Two years prior to current fiscal year	16,685	15,094
Three years prior to current fiscal year	15,032	12,827
Four years prior to current fiscal year	12,541	6,266
Prior	22,071	16,164
Total loans, net of unearned income	82,793	81,494
Consumer loans | Greater than or equal to 740 | Home equity line of credit (pre-reset)
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	1,728	1,873
Consumer loans | Greater than or equal to 740 | Home equity line of credit (post-reset)
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	72	69
Consumer loans | Greater than or equal to 740 | Home equity term loans
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	1
Three years prior to current fiscal year	1	2
Four years prior to current fiscal year	2	2
Prior	126	131
Total loans, net of unearned income	129	136
Consumer loans | Greater than or equal to 740 | Home equity loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	1,929	2,078
Consumer loans | Greater than or equal to 740 | Credit cards
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	75,979	81,168
Consumer loans | Greater than or equal to 740 | Credit cards
Financing Receivable, Credit Quality Indicator [Line Items]
Revolving loans converted to term loans	111	108
Total loans, net of unearned income	76,090	81,276
Consumer loans | Greater than or equal to 740 | Personal, small business and other
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	158	996
One year prior to current fiscal year	1,051	583
Two years prior to current fiscal year	481	128
Three years prior to current fiscal year	104	14
Four years prior to current fiscal year	11	8
Prior	158	168
Total loans, net of unearned income	1,963	1,897
Consumer loans | Classifiably managed
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	27,135	29,209
Consumer loans | Classifiably managed | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	17,128	17,007
Consumer loans | Classifiably managed | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	0	0
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 | Home equity loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	0	0
Consumer loans | Classifiably managed | Credit cards
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 | Personal, small business and other
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	27,135	29,209
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	17,128	17,007
Consumer loans | FICO not available
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	12,345	12,462
Consumer loans | FICO not available | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	7,837	7,763
Consumer loans | FICO not available | Home equity loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	43	5
Consumer loans | FICO not available | Credit cards
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	1,929	1,955
Consumer loans | FICO not available | Personal, small business and other
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	2,536	2,739
Consumer loans | Total loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	$ 305,364	$ 311,671