DERIVATIVES - Gains and Losses on Derivative Instruments Included in Statement of Operations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Change in fair value of open non-hedge derivative instruments:	$ (188)	$ 222	$ (84)
Gain (loss) on settlement of non-hedge derivative instruments:	80	(121)	6
Gain (loss) on derivative instruments	$ (108)	$ 101	$ (78)