LOANS - Corporate Loan Delinquency (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 687,722	$ 689,362
Loans at fair value	8,526	7,594
Unallocated portfolio layer cumulative basis adjustments	(213)	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	301,605	300,165
90 days  past due and accruing	498	594
Total non-accrual	998	1,882
Loans at fair value	8,232	7,281
Loans net of unearned income, before adjustments	301,628	300,072
Unallocated portfolio layer cumulative basis adjustments	(23)	93
Corporate loans | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	154,266	151,451
90 days  past due and accruing	377	426
Total non-accrual	404	717
Corporate loans | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	66,736	65,060
90 days  past due and accruing	7	16
Total non-accrual	38	51
Corporate loans | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	25,199	24,938
90 days  past due and accruing	23	69
Total non-accrual	454	868
Corporate loans | Lease financing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	267	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	46,928	51,067
90 days  past due and accruing	91	83
Total non-accrual	102	246
Corporate loans | 30–89 days past due
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	359	449
Corporate loans | 30–89 days past due | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	253	308
Corporate loans | 30–89 days past due | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	6	9
Corporate loans | 30–89 days past due | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	19	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	81	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	139	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	124	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	1	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	4	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	291,900	290,315
Corporate loans | Current | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	153,485	150,308
Corporate loans | Current | Financial institutions
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	66,691	64,993
Corporate loans | Current | Mortgage and real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	24,722	24,001
Corporate loans | Current | Lease financing
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	267	275
Corporate loans | Current | Other
Financing Receivable, Credit Quality Indicator [Line Items]
Loans, net of unearned income	$ 46,735	$ 50,738