SECURITIES - Schedule of Securities Pledged (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Pledged against derivatives, to qualify for fiduciary powers, and to secure public and other deposits as required by law
Financial Instruments Owned and Pledged as Collateral [Line Items]
Debt securities at amortized cost	$ 5,763	$ 4,816
Debt securities at fair value	5,351	4,782
Pledged as collateral for FHLB borrowing capacity
Financial Instruments Owned and Pledged as Collateral [Line Items]
Debt securities at amortized cost	245	325
Debt securities at fair value	225	333
Pledged against repurchase agreements
Financial Instruments Owned and Pledged as Collateral [Line Items]
Debt securities at amortized cost	0	1
Debt securities at fair value	$ 0	$ 1