ASSET IMPAIRMENT - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment		$ 1,671	$ 220,652	$ 1,292,308
Price curve, term		5 years		5 years
Increase (decrease) in commodity price assumptions (in percentage)				3.00%
Permian Basin unproved leasehold properties
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment	$ 208,300	$ 1,100
Permian Basin Unproved Leasehold Properties
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment		575	4,762	$ 29,168
San Juan Basin properties
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment	$ 7,500	0	7,519	133,055
San Juan Proved and Unproved Properties
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment				133,100
San Juan Basin unproved leasehold properties
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment		$ 0	$ 40	37,934
Oil MBbl
Impaired Long-Lived Assets Held and Used [Line Items]
Price curve, percent		3.00%
Increase (decrease) in commodity price assumptions (in percentage)	(5.00%)
Oil MBbl | Permian Basin unproved leasehold properties
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment				$ 1,092,200
Natural Gas
Impaired Long-Lived Assets Held and Used [Line Items]
Increase (decrease) in commodity price assumptions (in percentage)	(4.00%)