CREDIT QUALITY AND THE ALLOWANCE FOR CREDIT LOSSES - Troubled Debt Restructurings, Modified Default (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	$ 223	$ 164
Interest Rate Reduction
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	6	1
Term Extension
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	179	112
Payment Delay
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	34	44
Interest Rate Reduction and Term Extension
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	4	7
Commercial
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	173	145
Commercial | Interest Rate Reduction
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	1	0
Commercial | Term Extension
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	152	102
Commercial | Payment Delay
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	20	43
Commercial | Interest Rate Reduction and Term Extension
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	0	0
Commercial | Commercial and industrial
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	19	43
Commercial | Commercial and industrial | Interest Rate Reduction
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	1	0
Commercial | Commercial and industrial | Term Extension
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	18	0
Commercial | Commercial and industrial | Payment Delay
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	0	43
Commercial | Commercial and industrial | Interest Rate Reduction and Term Extension
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	0	0
Commercial | Commercial real estate
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	154	102
Commercial | Commercial real estate | Interest Rate Reduction
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	0	0
Commercial | Commercial real estate | Term Extension
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	134	102
Commercial | Commercial real estate | Payment Delay
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	20	0
Commercial | Commercial real estate | Interest Rate Reduction and Term Extension
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	0	0
Retail
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	50	19
Retail | Interest Rate Reduction
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	5	1
Retail | Term Extension
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	27	10
Retail | Payment Delay
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	14	1
Retail | Interest Rate Reduction and Term Extension
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	4	7
Retail | Residential mortgages
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	32	15
Retail | Residential mortgages | Interest Rate Reduction
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	0	1
Retail | Residential mortgages | Term Extension
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	26	9
Retail | Residential mortgages | Payment Delay
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	3	0
Retail | Residential mortgages | Interest Rate Reduction and Term Extension
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	3	5
Retail | Home equity
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	2	3
Retail | Home equity | Interest Rate Reduction
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	0	0
Retail | Home equity | Term Extension
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	1	1
Retail | Home equity | Payment Delay
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	0	0
Retail | Home equity | Interest Rate Reduction and Term Extension
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	1	2
Retail | Automobile
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	0	0
Retail | Automobile | Interest Rate Reduction
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	0	0
Retail | Automobile | Term Extension
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	0	0
Retail | Automobile | Payment Delay
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	0	0
Retail | Automobile | Interest Rate Reduction and Term Extension
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	0	0
Retail | Education
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	15	1
Retail | Education | Interest Rate Reduction
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	4	0
Retail | Education | Term Extension
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	0	0
Retail | Education | Payment Delay
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	11	1
Retail | Education | Interest Rate Reduction and Term Extension
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	0	0
Retail | Other retail
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	1	0
Retail | Other retail | Interest Rate Reduction
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	1	0
Retail | Other retail | Term Extension
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	0	0
Retail | Other retail | Payment Delay
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	0	0
Retail | Other retail | Interest Rate Reduction and Term Extension
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	$ 0	$ 0