EQUITY METHOD INTERESTS - Summary of Combined Statement of Operations Equity Method Interests (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Schedule of Equity Method Investments [Line Items]
Operating revenues	$ 596	$ 1,618	$ 1,875	$ 3,275
Operating expenses	942	1,489	6,589	2,757
Operating income	(190)	127	(4,493)	537
Net income	(378)	(316)	$ (5,000)	$ (318)
Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of Equity Method Investments [Line Items]
Operating revenues	351	52
Operating expenses	169	23
Operating income	182	29
Net income	159	21
Other comprehensive loss	$ (5)	$ (9)