ALLOWANCE FOR CREDIT LOSSES, NONACCRUAL LOANS AND LEASES, AND CONCENTRATIONS OF CREDIT RISK - Troubled Debt Restructurings (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
TDR's that defaulted within 12 months of modification date	$ 28	$ 37	$ 224	$ 89
Commercial | Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
TDR's that defaulted within 12 months of modification date	0	0	0	23
Retail | Residential mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
TDR's that defaulted within 12 months of modification date	28	37	224	66
Retail | Loans Insured or Guaranteed by US Government Authorities
Accounts, Notes, Loans and Financing Receivable [Line Items]
TDR's that defaulted within 12 months of modification date	$ 18	$ 34	$ 174	$ 37