ACQUISITIONS, DIVESTITURES AND OTHER TRANSACTIONS - PRO FORMA INFORMATION (Details) - Anadarko Petroleum Corporation $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) $ / shares
Business Acquisition [Line Items]
Revenues	$ 28,723
Net loss attributable to common stockholders	$ (769)
Net loss attributable to common stockholders per share—basic (in dollars per share) | $ / shares	$ (0.95)
Net loss attributable to common stockholders per share—diluted (in dollars per share) | $ / shares	$ (0.95)
Net loss attributable to common stockholders excluding pro-forma results of WES	$ (1,100)