INCOME TAXES - Narrative (Details) - USD ($)	3 Months Ended	12 Months Ended			24 Months Ended
	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2019	Nov. 29, 2018
Operating Loss Carryforwards [Line Items]
Change in enacted tax rate, amount		$ 0	$ 0	$ 68,000,000
Effective income tax rate		13.00%	15.10%
Net deferred tax liabilities		$ 1,744,000,000	$ 1,688,000,000		$ 1,744,000,000
Increase ff deferred tax liability due to adjustments to fair value of acquired assets		23,000,000
Operating loss carryforwards, subject to expiration		400,000,000			400,000,000
Operating loss carryforwards, not subject to expiration		1,300,000,000			1,300,000,000
Deferred tax assets, valuation allowance		7,000,000	14,000,000		7,000,000
Deferred tax liability includes deferred tax asset		134,000,000	94,000,000		134,000,000
Change in deferred tax asset due to change in tax status	$ 42,000,000	(42,000,000)	(73,000,000)	$ 0	115,000,000
Operating loss carryforwards		38,000,000			38,000,000
Net operating loss and credit carryforwards		453,000,000	155,000,000		453,000,000
Penalties associated with uncertain tax positions (less than)		0	0
Interest associated with uncertain tax positions		1,000,000	0
Energen
Operating Loss Carryforwards [Line Items]
Minimum tax credits, current income tax receivables		19,000,000			19,000,000
Minimum tax credits, noncurrent income tax receivables		19,000,000			19,000,000
Energen
Operating Loss Carryforwards [Line Items]
Business acquisition, deferred tax liabilities			$ 1,400,000,000			$ 1,425,000,000
Minimum tax credits, noncurrent income tax receivables						$ 76,000,000
Rattler MIdstream LP
Operating Loss Carryforwards [Line Items]
Net deferred tax liabilities		8,000,000			8,000,000
Net operating loss and credit carryforwards		$ 1,000,000			$ 1,000,000