EQUITY METHOD INTERESTS - Summary of Combined Statement of Operations Equity Method Interests (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Schedule of Equity Method Investments [Line Items]
Operating income	$ 595	$ (4,303)
Net income	459	(4,622)
Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of Equity Method Investments [Line Items]
Operating revenues	254	176
Operating income	112	86
Net income	89	77
Other comprehensive income (loss)	$ 4	$ (8)