EQUITY METHOD INTERESTS - Summary of Combined Statement of Operations Equity Method Interests (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Equity Method Investments and Joint Ventures [Abstract]
Operating revenues	$ 302	$ 2
Operating expenses	181	8
Operating income (loss)	121	(6)
Net income (loss)	115	(6)
Other comprehensive loss	$ (8)	$ 0