LOANS - Corporate Loan Delinquency (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 688,922	$ 689,362
Loans at fair value	8,106	7,594
Unallocated portfolio layer cumulative basis adjustments	299	93
Lease financing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	300	300
Corporate loans
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	299,771	300,165
90 days  past due and accruing	369	594
Total non-accrual	944	1,882
Loans at fair value	7,804	7,281
Loans net of unearned income, before adjustments	299,706	300,072
Unallocated portfolio layer cumulative basis adjustments	65	93
Corporate loans | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	154,111	151,451
90 days  past due and accruing	256	426
Total non-accrual	353	717
Corporate loans | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	64,388	65,060
90 days  past due and accruing	10	16
Total non-accrual	27	51
Corporate loans | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	26,252	24,938
90 days  past due and accruing	40	69
Total non-accrual	476	868
Corporate loans | Lease financing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	274	275
90 days  past due and accruing	0	0
Total non-accrual	0	0
Corporate loans | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	46,877	51,067
90 days  past due and accruing	63	83
Total non-accrual	88	246
Corporate loans | 30–89 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	279	449
Corporate loans | 30–89 days past due | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	177	308
Corporate loans | 30–89 days past due | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	10	9
Corporate loans | 30–89 days past due | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	39	66
Corporate loans | 30–89 days past due | Lease financing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	0	0
Corporate loans | 30–89 days past due | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	53	66
Corporate loans | Equal to and greater than 90 days past due and accruing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	90	145
Corporate loans | Equal to and greater than 90 days past due and accruing | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	79	118
Corporate loans | Equal to and greater than 90 days past due and accruing | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	0	7
Corporate loans | Equal to and greater than 90 days past due and accruing | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	1	3
Corporate loans | Equal to and greater than 90 days past due and accruing | Lease financing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	0	0
Corporate loans | Equal to and greater than 90 days past due and accruing | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	10	17
Corporate loans | Current
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	290,589	290,315
Corporate loans | Current | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	153,502	150,308
Corporate loans | Current | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	64,351	64,993
Corporate loans | Current | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	25,736	24,001
Corporate loans | Current | Lease financing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	274	275
Corporate loans | Current | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 46,726	$ 50,738