LOANS - Loan-to-Value Ratios Consumer Loans (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	$ 702,056	$ 694,488
Unallocated portfolio layer cumulative basis adjustments		(72)
Consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	386,312	393,102
Unallocated portfolio layer cumulative basis adjustments	231	(224)
Consumer loans | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	311,840	320,631
Consumer loans | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	72,995	71,378
Consumer loans | Less than or equal to 80% | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	107,142	107,142
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	8,650	8,742
Consumer loans | Greater than 100% | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	172	158
Consumer loans | LTV not available | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	1,725	1,692
Consumer loans | Total | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	117,689	117,734
Consumer loans | Residential mortgages | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	114,664	114,593
Consumer loans | Residential mortgages | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	24,326	24,456
Consumer loans | Residential mortgages | Less than or equal to 80% | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	1,440	9,196
One year prior to current fiscal year	9,238	13,973
Two years prior to current fiscal year	13,743	18,546
Three years prior to current fiscal year	18,488	18,247
Four years prior to current fiscal year	18,016	15,434
Prior	43,377	28,797
Total loans, net of unearned income	104,302	104,193
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	515	2,808
One year prior to current fiscal year	2,809	2,406
Two years prior to current fiscal year	2,342	2,579
Three years prior to current fiscal year	2,486	2,505
Four years prior to current fiscal year	2,409	1,739
Prior	8,999	7,642
Total loans, net of unearned income	$ 19,560	$ 19,679
Loan to value ratio	58.00%	58.00%
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	$ 548	$ 3,550
One year prior to current fiscal year	3,392	2,036
Two years prior to current fiscal year	1,877	2,078
Three years prior to current fiscal year	1,847	472
Four years prior to current fiscal year	446	226
Prior	513	351
Total loans, net of unearned income	8,623	8,713
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	50	421
One year prior to current fiscal year	406	654
Two years prior to current fiscal year	580	462
Three years prior to current fiscal year	362	426
Four years prior to current fiscal year	317	326
Prior	451	148
Total loans, net of unearned income	2,166	2,437
Consumer loans | Residential mortgages | Greater than 100% | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	1
One year prior to current fiscal year	4	2
Two years prior to current fiscal year	2	42
Three years prior to current fiscal year	52	33
Four years prior to current fiscal year	36	1
Prior	27	25
Total loans, net of unearned income	121	104
Consumer loans | Residential mortgages | Greater than 100% | In offices outside North America
Financing Receivable, Credit Quality Indicator [Line Items]
Current fiscal year	0	0
One year prior to current fiscal year	0	412
Two years prior to current fiscal year	460	698
Three years prior to current fiscal year	785	657
Four years prior to current fiscal year	754	176
Prior	192	8
Total loans, net of unearned income	2,191	1,951
Consumer loans | Residential mortgages | LTV not available | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	1,618	1,583
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	409	389
Consumer loans | Home equity loans | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	3,025	3,141
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	2,840	2,949
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	27	29
Consumer loans | Home equity loans | Greater than 100% | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	51	54
Consumer loans | Home equity loans | LTV not available | UNITED STATES
Financing Receivable, Credit Quality Indicator [Line Items]
Total loans, net of unearned income	107	109
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	2,420	2,514
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	24	26
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	42	45
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	420	435
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	3	3
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	$ 9