VARIABLE INTEREST ENTITIES - Affordable Housing Tax Credit Investments And Related Unfunded Commitments (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Proportional amortization method investments included in other assets	$ 66	$ 55
Equity method investments included in other assets	4	5
Total LIHTC investments included in other assets	70	60
Unfunded LIHTC commitments	$ 47	$ 60