DERIVATIVES ACTIVITIES - Cumulative Basis Adjustment (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Debt securities AFS, carrying amount of hedged asset	$ 94,659	$ 81,632
Debt securities AFS, cumulative fair value hedging adjustment increasing (decreasing) the carrying amount, active	(114)	(196)
Debt securities AFS, cumulative fair value hedging adjustment increasing (decreasing) the carrying amount, de-designated	743	295
Long-term debt, carrying amount of hedged liability	157,387	149,054
Long-term debt, cumulative fair value hedging adjustment increasing (decreasing) the carrying amount, active	2,334	1,211
Long-term debt, cumulative fair value hedging adjustment increasing (decreasing) the carrying amount, de-designated	3,445	$ 869
Cumulative basis adjustment within active hedges	(8)
Cumulative basis adjustment within de-designated hedges	157
Amount of designated hedged items	605
Carrying value of closed portfolios used in hedging relations	$ 20,000