DERIVATIVES ACTIVITIES - Cumulative Basis Adjustment (Details) $ in Millions	Mar. 31, 2018 USD ($)
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Long-term debt, carrying amount of hedged asset (liability)	$ 139,786
Long-term debt, cumulative fair value hedging adjustment included in the carrying amount, active	(24)
Long-term debt, cumulative fair value hedging adjustment included in the carrying amount, de-designated	1,921
Investments available for sale, carrying amount of hedged asset (liability)	73,717
Investments available for sale, cumulative fair value hedging adjustment included in the carrying amount, active	259
Investments available for sale, cumulative fair value hedging adjustment included in the carrying amount, de-designated	$ 69