LOANS - Corporate Loan Delinquency (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Financing Receivable, Credit Quality Indicator [Line Items]
Loans at fair value	$ 8,165	$ 8,040
Unallocated portfolio layer cumulative basis adjustments		(72)
Corporate loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total past due and accruing	493	313
Total non-accrual	1,376	1,377
Loans at fair value	7,887	7,759
Loans net of unearned income, before adjustments	315,724	301,458
Unallocated portfolio layer cumulative basis adjustments	20	(72)
Corporate loans | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total past due and accruing	267	218
Total non-accrual	611	542
Corporate loans, net of unearned income	157,252	148,674
Corporate loans | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Total past due and accruing	72	8
Total non-accrual	74	73
Corporate loans, net of unearned income	73,913	68,378
Corporate loans | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total past due and accruing	114	8
Total non-accrual	609	567
Corporate loans, net of unearned income	26,436	26,546
Corporate loans | Lease financing
Financing Receivable, Credit Quality Indicator [Line Items]
Total past due and accruing	1	1
Total non-accrual	21	0
Corporate loans, net of unearned income	277	276
Corporate loans | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Total past due and accruing	39	78
Total non-accrual	61	195
Corporate loans, net of unearned income	49,959	49,825
Corporate loans | 30–89 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Total past due and accruing	341	259
Corporate loans | 30–89 days past due | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total past due and accruing	203	183
Corporate loans | 30–89 days past due | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Total past due and accruing	51	8
Corporate loans | 30–89 days past due | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total past due and accruing	61	6
Corporate loans | 30–89 days past due | Lease financing
Financing Receivable, Credit Quality Indicator [Line Items]
Total past due and accruing	0	0
Corporate loans | 30–89 days past due | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Total past due and accruing	26	62
Corporate loans | Equal to and greater than 90 days past due and accruing
Financing Receivable, Credit Quality Indicator [Line Items]
Total past due and accruing	152	54
Corporate loans | Equal to and greater than 90 days past due and accruing | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total past due and accruing	64	35
Corporate loans | Equal to and greater than 90 days past due and accruing | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Total past due and accruing	21	0
Corporate loans | Equal to and greater than 90 days past due and accruing | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total past due and accruing	53	2
Corporate loans | Equal to and greater than 90 days past due and accruing | Lease financing
Financing Receivable, Credit Quality Indicator [Line Items]
Total past due and accruing	1	1
Corporate loans | Equal to and greater than 90 days past due and accruing | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Total past due and accruing	13	16
Corporate loans | Current
Financing Receivable, Credit Quality Indicator [Line Items]
Corporate loans, net of unearned income	305,968	292,009
Corporate loans | Current | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Corporate loans, net of unearned income	156,374	147,914
Corporate loans | Current | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Corporate loans, net of unearned income	73,767	68,297
Corporate loans | Current | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Corporate loans, net of unearned income	25,713	25,971
Corporate loans | Current | Lease financing
Financing Receivable, Credit Quality Indicator [Line Items]
Corporate loans, net of unearned income	255	275
Corporate loans | Current | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Corporate loans, net of unearned income	$ 49,859	$ 49,552