DERIVATIVE INSTRUMENTS - Fair Value and Notional Amounts of Derivatives With Counterparty Credit Risk (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Notional Amount of Derivatives	$ 31,023	$ 25,751
Asset Derivatives Fair Value	430	331
Liability Derivatives Fair Value	(497)	(474)
AA
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Notional Amount of Derivatives	5,207	4,708
Asset Derivatives Fair Value	79	52
Liability Derivatives Fair Value	(42)	(37)
A
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Notional Amount of Derivatives	25,378	20,604
Asset Derivatives Fair Value	345	271
Liability Derivatives Fair Value	(401)	(370)
BBB
Derivative Instruments and Hedging Activities Disclosure [Line Items]
Notional Amount of Derivatives	438	439
Asset Derivatives Fair Value	6	8
Liability Derivatives Fair Value	$ (54)	$ (67)