LOANS AND LEASES - Non-Performing Assets (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	$ 110	$ 170
Non-Performing [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Non-accrual loans	110	170
Total non-performing loans	110	170
Other real estate owned	8	10
Non Performing Assets	$ 118	$ 180
Non-performing loans / total loans and leases	0.45%	0.67%
Non-performing assets + 90 days past due + OREO / total loans and leases + OREO	0.51%	0.77%
Past due	90 days	90 days