VARIABLE INTEREST ENTITIES - Affordable Housing Tax Credit Investments And Related Unfunded Commitments (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Proportional amortization method investments included in other assets	$ 74	$ 71
Equity method investments included in other assets	2	3
Total LIHTC investments included in other assets	76	74
Unfunded LIHTC commitments	$ 37	$ 45