ALLOWANCE FOR CREDIT LOSSES, NONACCRUAL LOANS AND LEASES, AND CONCENTRATIONS OF CREDIT RISK - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Financing Receivable, Troubled Debt Restructuring [Line Items]
Net charge-offs	$ 133	$ 59
Credit provision	168	3
Increase to ACL	35
Loans and leases	154,688		$ 156,662
Mortgage loans collateralized by OREO	293		250
TDR commitment to lend			81
Charge-offs	171	101
Troubled Debt Restructuring
Financing Receivable, Troubled Debt Restructuring [Line Items]
Charge-offs		1
Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Net charge-offs	52	11
Loans and leases	80,866		82,180
Charge-offs	59	14
Retail
Financing Receivable, Troubled Debt Restructuring [Line Items]
Net charge-offs	81	48
Loans and leases	73,822		74,482
Charge-offs	112	$ 87
Commercial and industrial | Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans and leases	50,450		51,836
Charge-offs	55
Collateral Dependent | Home Equity Loan and Residential Mortgages | Retail
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans and leases	556		561
Collateral Dependent | Commercial and industrial | Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans and leases	$ 115		$ 21