LOANS - Loan-to-Value Ratios Consumer Loans (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	$ 666,348	$ 657,221
Consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	377,714	368,067
Consumer loans | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	75,261	79,053
Consumer loans | Less than or equal to 80% | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	100,403	90,741
Consumer loans | Greater than 80% but less than or equal to 100% | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	8,033	8,385
Consumer loans | Greater than 100% | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	204	263
Consumer loans | LTV not available | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	1,525	1,230
Consumer loans | Total | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	110,165	100,619
Consumer loans | Residential mortgages
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	106,369	96,039
Consumer loans | Residential mortgages | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	106,369	96,039
Consumer loans | Residential mortgages | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	26,389	28,114
Consumer loans | Residential mortgages | Less than or equal to 80% | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	11,461	15,644
One year prior to current fiscal year	17,794	19,104
Two years prior to current fiscal year	19,047	16,935
Three years prior to current fiscal year	16,325	8,789
Four years prior to current fiscal year	8,306	3,598
Prior	24,138	22,367
Total loans, net of unearned income	97,071	86,437
Consumer loans | Residential mortgages | Less than or equal to 80% | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	2,304	3,106
One year prior to current fiscal year	3,303	4,144
Two years prior to current fiscal year	3,467	3,293
Three years prior to current fiscal year	2,494	3,048
Four years prior to current fiscal year	2,622	2,074
Prior	8,322	9,201
Total loans, net of unearned income	$ 22,512	$ 24,866
Loan to value ratio	53.00%	51.00%
Consumer loans | Residential mortgages | Greater than 80% but less than or equal to 100% | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	$ 2,668	$ 6,497
One year prior to current fiscal year	4,057	1,227
Two years prior to current fiscal year	663	267
Three years prior to current fiscal year	241	140
Four years prior to current fiscal year	182	74
Prior	197	132
Total loans, net of unearned income	8,008	8,337
Consumer loans | Residential mortgages | Greater than 80% but less than or equal to 100% | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	883	975
One year prior to current fiscal year	957	964
Two years prior to current fiscal year	928	502
Three years prior to current fiscal year	446	92
Four years prior to current fiscal year	68	48
Prior	45	36
Total loans, net of unearned income	3,327	2,617
Consumer loans | Residential mortgages | Greater than 100% | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	8	40
One year prior to current fiscal year	42	33
Two years prior to current fiscal year	33	1
Three years prior to current fiscal year	1	23
Four years prior to current fiscal year	26	9
Prior	75	74
Total loans, net of unearned income	185	180
Consumer loans | Residential mortgages | Greater than 100% | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	294
One year prior to current fiscal year	187	273
Two years prior to current fiscal year	187	25
Three years prior to current fiscal year	0	1
Four years prior to current fiscal year	0	0
Prior	3	7
Total loans, net of unearned income	377	600
Consumer loans | Residential mortgages | LTV not available | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	1,105	1,085
Consumer loans | Residential mortgages | LTV not available | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	173	31
Consumer loans | Home equity loans (pre-reset) | Less than or equal to 80% | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	2,846	3,677
Consumer loans | Home equity loans (pre-reset) | Greater than 80% but less than or equal to 100% | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	19	36
Consumer loans | Home equity loans (pre-reset) | Greater than 100% | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	7	56
Consumer loans | Home equity loans (post-reset) | Less than or equal to 80% | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	486	627
Consumer loans | Home equity loans (post-reset) | Greater than 80% but less than or equal to 100% | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	6	12
Consumer loans | Home equity loans (post-reset) | Greater than 100% | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	12	27
Consumer loans | Home equity loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	3,796	4,580
Consumer loans | Home equity loans | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	3,796	4,580
Consumer loans | Home equity loans | Less than or equal to 80% | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	3,332	4,304
Consumer loans | Home equity loans | Greater than 80% but less than or equal to 100% | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	25	48
Consumer loans | Home equity loans | Greater than 100% | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	19	83
Consumer loans | Home equity loans | LTV not available | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	$ 420	$ 145