CREDIT QUALITY AND THE ALLOWANCE FOR CREDIT LOSSES - Troubled Debt Restructurings, Modified Default (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	$ 58	$ 128	$ 160	$ 224
Interest Rate Reduction
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	3	3	4	6
Term Extension
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	48	89	140	166
Payment Delay
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	4	21	8	34
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		7	2
Term Extension and Payment Delay
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	0	15	1	16
Commercial
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	40	115	122	181
Commercial | Interest Rate Reduction
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	0	1	0	1
Commercial | Term Extension
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	40	78	120	144
Commercial | Payment Delay
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	0	21	2	21
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	0
Commercial | Term Extension and Payment Delay
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	0	15	0	15
Commercial | Commercial and industrial
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	36	19	48	19
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	0	1	0	1
Commercial | Commercial and industrial | Term Extension
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	36	3	48	3
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	0	0	0
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	0
Commercial | Commercial and industrial | Term Extension and Payment Delay
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	0	15	0	15
Commercial | Commercial real estate
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	4	96	74	162
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	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	4	75	72	141
Commercial | Commercial real estate | Payment Delay
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	0	21	2	21
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	0
Commercial | Commercial real estate | Term Extension and Payment Delay
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	0	0	0	0
Retail
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	18	13	38	43
Retail | Interest Rate Reduction
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	3	2	4	5
Retail | Term Extension
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	8	11	20	22
Retail | Payment Delay
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	4	0	6	13
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	3		7	2
Retail | Term Extension and Payment Delay
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	0	0	1	1
Retail | Residential mortgages
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	16	11	33	25
Retail | Residential mortgages | Interest Rate Reduction
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	1	0	1	0
Retail | Residential mortgages | Term Extension
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	8	11	20	22
Retail | Residential mortgages | Payment Delay
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	4	0	5	1
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		6	1
Retail | Residential mortgages | Term Extension and Payment Delay
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	0	0	1	1
Retail | Home equity
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	0	0	3	1
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	1	0
Retail | Home equity | Term Extension
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	0	0	0	0
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	1	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	0		1	1
Retail | Home equity | Term Extension and Payment Delay
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	0	0	0	0
Retail | Education
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	1	1	1	16
Retail | Education | Interest Rate Reduction
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	1	1	1	4
Retail | Education | Term Extension
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	0	0	0	0
Retail | Education | Payment Delay
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	0	0	0	12
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	0
Retail | Education | Term Extension and Payment Delay
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	0	0	0	0
Retail | Other retail
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	1	1	1	1
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	1	1	1
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	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	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	0
Retail | Other retail | Term Extension and Payment Delay
Financing Receivable, Modified, Subsequent Default [Line Items]
Amortized cost basis of modified loans that are in subsequent default	$ 0	$ 0	$ 0	$ 0