LOANS - Consumer Loans Credit Scores (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	$ 687,722	$ 689,362
Unallocated portfolio layer cumulative basis adjustments	(213)	93
Consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	386,117	389,197
Unallocated portfolio layer cumulative basis adjustments	(38)
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	312,833	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	2,892	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	26,200	29,200
Consumer loans | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	73,322	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	306	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	17,500	17,000
Consumer loans | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	311,381	311,671
Consumer loans | Residential mortgages | In North America offices
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	112,710	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	321	294
Consumer loans | Residential mortgages | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	25,489	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	65	69
Consumer loans | Residential mortgages | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	112,710	108,711
Consumer loans | Home equity loans | In North America offices
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	3,338	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	82	85
Consumer loans | Home equity loans | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	3,338	3,592
Consumer loans | Credit cards | In North America offices
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	163,467	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	2,445	2,461
Consumer loans | Credit cards | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Revolving loans converted to term loans	33	51
Total loans, net of unearned income	13,197	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	205	227
Consumer loans | Credit cards | Canada
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	609	610
Consumer loans | Credit cards | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	162,858	164,110
Consumer loans | Personal, small business and other
Financing Receivable, Credit Quality Indicator [Line Items]
Revolving loans converted to term loans	28	37
Consumer loans | Personal, small business and other | In North America offices
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	33,318	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	44	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	34,636	$ 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	36	$ 40
Consumer loans | Personal, small business and other | Canada
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	843	877
Consumer loans | Personal, small business and other | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	32,475	35,258
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	74,700	77,500
Consumer loans | Less than 660 | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	26,442	26,297
Consumer loans | Less than 660 | Residential mortgages | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	48	163
One year prior to current fiscal year	204	339
Two years prior to current fiscal year	387	270
Three years prior to current fiscal year	336	232
Four years prior to current fiscal year	250	138
Prior	1,596	1,377
Total loans, net of unearned income	2,821	2,519
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	295	300
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	62	61
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	2
Four years prior to current fiscal year	0	0
Prior	51	54
Total loans, net of unearned income	51	56
Consumer loans | Less than 660 | Home equity loans | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	408	417
Consumer loans | Less than 660 | Credit cards | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	21,559	21,899
Consumer loans | Less than 660 | Credit cards | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Revolving loans converted to term loans	1,190	1,011
Total loans, net of unearned income	22,749	22,910
Consumer loans | Less than 660 | Personal, small business and other | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	25	88
One year prior to current fiscal year	133	204
Two years prior to current fiscal year	167	52
Three years prior to current fiscal year	39	6
Four years prior to current fiscal year	4	5
Prior	96	96
Total loans, net of unearned income	464	451
Consumer loans | 660 to 739 | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	77,164	76,958
Consumer loans | 660 to 739 | Residential mortgages | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	1,068	2,758
One year prior to current fiscal year	2,880	3,423
Two years prior to current fiscal year	3,283	3,107
Three years prior to current fiscal year	2,906	2,143
Four years prior to current fiscal year	2,163	1,382
Prior	5,143	4,122
Total loans, net of unearned income	17,443	16,935
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	816	905
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	79	76
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	1
Four years prior to current fiscal year	1	1
Prior	99	109
Total loans, net of unearned income	100	111
Consumer loans | 660 to 739 | Home equity loans | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	995	1,092
Consumer loans | 660 to 739 | Credit cards | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	57,179	57,479
Consumer loans | 660 to 739 | Credit cards | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Revolving loans converted to term loans	560	490
Total loans, net of unearned income	57,739	57,969
Consumer loans | 660 to 739 | Personal, small business and other | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	147	343
One year prior to current fiscal year	363	351
Two years prior to current fiscal year	256	83
Three years prior to current fiscal year	58	9
Four years prior to current fiscal year	5	7
Prior	158	169
Total loans, net of unearned income	987	962
Consumer loans | Greater than or equal to 740 | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	168,822	166,745
Consumer loans | Greater than or equal to 740 | Residential mortgages | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	5,728	14,309
One year prior to current fiscal year	13,688	16,834
Two years prior to current fiscal year	16,506	15,094
Three years prior to current fiscal year	14,867	12,827
Four years prior to current fiscal year	12,471	6,266
Prior	21,546	16,164
Total loans, net of unearned income	84,806	81,494
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	1,687	1,873
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	73	69
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	1
Three years prior to current fiscal year	1	2
Four years prior to current fiscal year	2	2
Prior	119	131
Total loans, net of unearned income	122	136
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	1,882	2,078
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	79,982	81,168
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	117	108
Total loans, net of unearned income	80,099	81,276
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	514	996
One year prior to current fiscal year	863	583
Two years prior to current fiscal year	406	128
Three years prior to current fiscal year	86	14
Four years prior to current fiscal year	8	8
Prior	158	168
Total loans, net of unearned income	2,035	1,897
Consumer loans | Classifiably managed | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	17,472	17,007
Consumer loans | Classifiably managed | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	26,236	29,209
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	17,472	17,007
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	26,236	29,209
Consumer loans | FICO not available | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	12,717	12,462
Consumer loans | FICO not available | Residential mortgages | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	7,640	7,763
Consumer loans | FICO not available | Home equity loans | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	53	5
Consumer loans | FICO not available | Credit cards | U.S. plans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	2,271	1,955
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	$ 2,753	$ 2,739