FAIR VALUE MEASUREMENTS (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Original Carrying Value | Midstream
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unproved oil and gas properties	$ 31,023	$ 816,282
Proved oil and gas properties	700,182	1,895,670
Operating lease right-of-use assets, net	13,514	0
Other long-term assets(1)	51,518	0
Equity method investment	0	17,063
Midstream property, plant and equipment	432,415	474,529
Intangible assets	0	394,999
Goodwill	0	691,970
Total	1,228,652	4,290,513
Estimated Fair Value | Alta Mesa RBL | 7.875% Senior Unsecured Notes Due 2024
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of unsecured senior notes	45,300	312,500
Estimated Fair Value | Midstream
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unproved oil and gas properties	0	74,217
Proved oil and gas properties	215,352	604,023
Operating lease right-of-use assets, net	0	0
Other long-term assets(1)	24,189	0
Equity method investment	0	1,100
Midstream property, plant and equipment	83,818	406,122
Intangible assets	0	0
Goodwill	0	0
Total	323,359	1,085,462
Impairment | Midstream
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unproved oil and gas properties	31,023	742,065
Proved oil and gas properties	484,830	1,291,647
Operating lease right-of-use assets, net	13,514	0
Other long-term assets(1)	27,329	0
Equity method investment	0	15,963
Midstream property, plant and equipment	348,597	68,407
Intangible assets	0	394,999
Goodwill	0	691,970
Total	$ 905,293	$ 3,205,051