DERIVATIVE INSTRUMENTS - Fair Value and Notional Amounts of Derivatives With Counterparty Credit Risk (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Notional Amount of Derivatives	$ 27,220	$ 25,751
Asset Derivatives Fair Value	797	331
Liability Derivatives Fair Value	(353)	(474)
AA
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Notional Amount of Derivatives	4,685	4,708
Asset Derivatives Fair Value	123	52
Liability Derivatives Fair Value	(12)	(37)
A
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Notional Amount of Derivatives	22,081	20,604
Asset Derivatives Fair Value	673	271
Liability Derivatives Fair Value	(290)	(370)
BBB
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Notional Amount of Derivatives	454	439
Asset Derivatives Fair Value	1	8
Liability Derivatives Fair Value	$ (51)	$ (67)