LOANS - Loan-to-Value Ratios Consumer Loans (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 | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	311,381	311,671
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 | Less than or equal to 80% | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	106,517	101,290
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	7,523	9,119
Consumer loans | Greater than 100% | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	154	207
Consumer loans | LTV not available | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	1,854	1,687
Consumer loans | Total | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	116,048	112,303
Consumer loans | Residential mortgages | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	112,710	108,711
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 | Less than or equal to 80% | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	5,408	13,907
One year prior to current fiscal year	14,753	17,736
Two years prior to current fiscal year	18,717	18,795
Three years prior to current fiscal year	18,620	16,094
Four years prior to current fiscal year	15,790	8,198
Prior	30,067	23,120
Total loans, net of unearned income	103,355	97,850
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	1,584	2,756
One year prior to current fiscal year	2,597	3,229
Two years prior to current fiscal year	2,859	3,257
Three years prior to current fiscal year	2,821	2,286
Four years prior to current fiscal year	1,971	2,525
Prior	8,939	8,000
Total loans, net of unearned income	$ 20,771	$ 22,053
Loan to value ratio	56.00%	55.00%
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	$ 1,463	$ 3,769
One year prior to current fiscal year	2,461	3,900
Two years prior to current fiscal year	2,445	728
Three years prior to current fiscal year	506	306
Four years prior to current fiscal year	254	191
Prior	362	191
Total loans, net of unearned income	7,491	9,085
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	267	1,007
One year prior to current fiscal year	840	807
Two years prior to current fiscal year	674	754
Three years prior to current fiscal year	670	454
Four years prior to current fiscal year	379	84
Prior	156	84
Total loans, net of unearned income	2,986	3,190
Consumer loans | Residential mortgages | Greater than 100% | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	3
One year prior to current fiscal year	2	52
Two years prior to current fiscal year	32	33
Three years prior to current fiscal year	33	1
Four years prior to current fiscal year	1	26
Prior	26	23
Total loans, net of unearned income	94	138
Consumer loans | Residential mortgages | Greater than 100% | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	112
One year prior to current fiscal year	246	439
Two years prior to current fiscal year	515	382
Three years prior to current fiscal year	426	62
Four years prior to current fiscal year	125	2
Prior	7	3
Total loans, net of unearned income	1,319	1,000
Consumer loans | Residential mortgages | LTV not available | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	1,770	1,638
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	413	183
Consumer loans | Home equity loans | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	3,338	3,592
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	3,162	3,440
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	32	34
Consumer loans | Home equity loans | Greater than 100% | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	60	69
Consumer loans | Home equity loans | LTV not available | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	84	49
Consumer loans | Home equity line of credit (pre-reset) | Less than or equal to 80% | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	2,702	2,964
Consumer loans | Home equity line of credit (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	28	29
Consumer loans | Home equity line of credit (pre-reset) | Greater than 100% | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	50	57
Consumer loans | Home equity line of credit (post-reset) | Less than or equal to 80% | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	460	476
Consumer loans | Home equity line of credit (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	4	5
Consumer loans | Home equity line of credit (post-reset) | Greater than 100% | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	$ 10	$ 12