CREDIT QUALITY AND THE ALLOWANCE FOR CREDIT LOSSES - Troubled Debt Restructuring Activity (Details) $ in Millions	12 Months Ended
	Dec. 31, 2022 USD ($) contract
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | contract	5,846
Amortized Cost	$ 501
Interest Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized Cost	68
Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized Cost	124
Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized Cost	$ 309
Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | contract	29
Amortized Cost	$ 26
Commercial | Interest Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized Cost	0
Commercial | Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized Cost	26
Commercial | Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized Cost	$ 0
Commercial | Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | contract	29
Amortized Cost	$ 26
Commercial | Commercial and industrial | Interest Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized Cost	0
Commercial | Commercial and industrial | Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized Cost	26
Commercial | Commercial and industrial | Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized Cost	$ 0
Retail
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | contract	5,817
Amortized Cost	$ 475
Retail | Interest Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized Cost	68
Retail | Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized Cost	98
Retail | Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized Cost	$ 309
Retail | Residential mortgages
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | contract	1,884
Amortized Cost	$ 408
Retail | Residential mortgages | Interest Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized Cost	52
Retail | Residential mortgages | Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized Cost	96
Retail | Residential mortgages | Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized Cost	$ 260
Retail | Home equity
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | contract	381
Amortized Cost	$ 25
Retail | Home equity | Interest Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized Cost	4
Retail | Home equity | Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized Cost	2
Retail | Home equity | Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized Cost	$ 19
Retail | Automobile
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | contract	601
Amortized Cost	$ 6
Retail | Automobile | Interest Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized Cost	2
Retail | Automobile | Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized Cost	0
Retail | Automobile | Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized Cost	$ 4
Retail | Education
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | contract	631
Amortized Cost	$ 25
Retail | Education | Interest Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized Cost	0
Retail | Education | Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized Cost	0
Retail | Education | Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized Cost	$ 25
Retail | Other retail
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Contracts | contract	2,320
Amortized Cost	$ 11
Retail | Other retail | Interest Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized Cost	10
Retail | Other retail | Term Extension
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized Cost	0
Retail | Other retail | Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Amortized Cost	$ 1