INCOME TAXES - Components of Income Tax Provision (Benefit) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current income tax provision (benefit):
Federal									$ 0	$ 0	$ 0
State									0	0	0
Total current income tax provision (benefit)									0	0	0
Deferred income tax provision (benefit):
Federal									40	160	(21)
State									7	8	1
Total deferred income tax provision (benefit)									47	168	(20)
Provision for (benefit from) income taxes	$ (124)	$ 102	$ 102	$ (33)	$ 85	$ 43	$ (7)	$ 47	$ 47	$ 168	$ (20)