DERIVATIVES - Cumulative Basis Adjustments for Fair Value Hedges (Details) - Fair Value Hedging - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Securities due within one year
Derivative [Line Items]
Carrying Amount of the Hedged Item	$ 0	$ (599)
Cumulative Amount of Fair Value Hedging Adjustment included in Carrying Amount of the Hedged Item	0	0
Long-term debt
Derivative [Line Items]
Carrying Amount of the Hedged Item	(1,517)	(1,494)
Cumulative Amount of Fair Value Hedging Adjustment included in Carrying Amount of the Hedged Item	$ (20)	$ 3