INCOME TAXES - Summary of Valuation Allowance Against Certain Foreign Net Deferred Tax Assets and State Net Operating Losses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Movement in Valuation Allowance of Deferred Tax Assets [Roll Forward]
Balance at beginning of year	$ 3,947	$ 3,816	$ 5,401
State	41	15	139
U.S.	971	124	905
Foreign	0	(8)	(2,629)
Balance at end of year	$ 4,959	$ 3,947	$ 3,816