LOANS - Loan-to-Value Ratios Consumer Loans (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	$ 688,922	$ 689,362
Unallocated portfolio layer cumulative basis adjustments	299	93
Consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	389,151	389,197
Unallocated portfolio layer cumulative basis adjustments	670
Consumer loans | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	312,924	311,671
Consumer loans | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	74,106	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	107,932	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	7,455	9,119
Consumer loans | Greater than 100% | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	173	207
Consumer loans | LTV not available | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	1,808	1,687
Consumer loans | Total | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	117,368	112,303
Consumer loans | Residential mortgages | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	114,126	108,711
Consumer loans | Residential mortgages | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	25,702	26,426
Consumer loans | Residential mortgages | Less than or equal to 80% | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	7,881	13,907
One year prior to current fiscal year	14,646	17,736
Two years prior to current fiscal year	18,864	18,795
Three years prior to current fiscal year	18,448	16,094
Four years prior to current fiscal year	15,587	8,198
Prior	29,438	23,120
Total loans, net of unearned income	104,864	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	2,339	2,756
One year prior to current fiscal year	2,592	3,229
Two years prior to current fiscal year	2,812	3,257
Three years prior to current fiscal year	2,744	2,286
Four years prior to current fiscal year	1,903	2,525
Prior	8,487	8,000
Total loans, net of unearned income	$ 20,877	$ 22,053
Loan to value ratio	57.00%	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	$ 2,203	$ 3,769
One year prior to current fiscal year	2,130	3,900
Two years prior to current fiscal year	1,987	728
Three years prior to current fiscal year	467	306
Four years prior to current fiscal year	264	191
Prior	373	191
Total loans, net of unearned income	7,424	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	383	1,007
One year prior to current fiscal year	677	807
Two years prior to current fiscal year	515	754
Three years prior to current fiscal year	456	454
Four years prior to current fiscal year	335	84
Prior	164	84
Total loans, net of unearned income	2,530	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	54	33
Three years prior to current fiscal year	33	1
Four years prior to current fiscal year	1	26
Prior	25	23
Total loans, net of unearned income	115	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	402	439
Two years prior to current fiscal year	670	382
Three years prior to current fiscal year	639	62
Four years prior to current fiscal year	174	2
Prior	9	3
Total loans, net of unearned income	1,894	1,000
Consumer loans | Residential mortgages | LTV not available | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	1,723	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	401	183
Consumer loans | Home equity loans | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	3,242	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	3,068	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	31	34
Consumer loans | Home equity loans | Greater than 100% | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	58	69
Consumer loans | Home equity loans | LTV not available | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	85	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	2,619	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	27	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	49	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	449	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	$ 9	$ 12