DERIVATIVE INSTRUMENTS - Fair Value and Notional Amounts of Derivatives With Counterparty Credit Risk (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Notional Amount of Derivatives	$ 28,803	$ 25,751
Asset Derivatives Fair Value	457	331
Liability Derivatives Fair Value	(367)	(474)
AA
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Notional Amount of Derivatives	5,122	4,708
Asset Derivatives Fair Value	78	52
Liability Derivatives Fair Value	(12)	(37)
A
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Notional Amount of Derivatives	23,237	20,604
Asset Derivatives Fair Value	375	271
Liability Derivatives Fair Value	(302)	(370)
BBB
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Notional Amount of Derivatives	444	439
Asset Derivatives Fair Value	4	8
Liability Derivatives Fair Value	$ (53)	$ (67)