EQUITY METHOD INTERESTS - Rollforward Activity (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Movement In Equity Method Interests [Roll Forward]
Balance at December 31, 2018	$ 121
Acquisitions	118	$ 0
Balance at March 31, 2019	209
Altus Midstream Company
Movement In Equity Method Interests [Roll Forward]
Balance at December 31, 2018	91
Acquisitions	52
Contributions	66
Balance at March 31, 2019	209
Altus Midstream Company | Gulf Coast Express Pipeline LLC
Movement In Equity Method Interests [Roll Forward]
Balance at December 31, 2018	91
Acquisitions	0
Contributions	66
Balance at March 31, 2019	157
Altus Midstream Company | EPIC Crude Holdings, LP
Movement In Equity Method Interests [Roll Forward]
Balance at December 31, 2018	0
Acquisitions	52
Contributions	0
Balance at March 31, 2019	$ 52