DEFERRED REVENUE - Rollforward of deferred revenue (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($)
Movement in Deferred Revenue [Roll Forward]
Current deferred revenue, beginning balance	$ 11,467
Current deferred revenue, Additions	6,388
Current deferred revenue, Less revenue recognized	6,216
Current deferred revenue, ending balance	11,639
Noncurrent deferred revenue, beginning balance	39,504
Noncurrent deferred revenue, Additions	5,199
Noncurrent deferred revenue, Less reclassification to current deferred revenue	3,500
Noncurrent deferred revenue, ending balance	41,203
Utica Shale
Movement in Deferred Revenue [Roll Forward]
Current deferred revenue, beginning balance	18
Current deferred revenue, Additions	5
Current deferred revenue, Less revenue recognized	5
Current deferred revenue, ending balance	18
Noncurrent deferred revenue, beginning balance	21
Noncurrent deferred revenue, Additions	0
Noncurrent deferred revenue, Less reclassification to current deferred revenue	5
Noncurrent deferred revenue, ending balance	16
Williston Basin
Movement in Deferred Revenue [Roll Forward]
Current deferred revenue, beginning balance	1,414
Current deferred revenue, Additions	350
Current deferred revenue, Less revenue recognized	364
Current deferred revenue, ending balance	1,400
Noncurrent deferred revenue, beginning balance	4,393
Noncurrent deferred revenue, Additions	1,701
Noncurrent deferred revenue, Less reclassification to current deferred revenue	787
Noncurrent deferred revenue, ending balance	5,307
Piceance Basin
Movement in Deferred Revenue [Roll Forward]
Current deferred revenue, beginning balance	7,616
Current deferred revenue, Additions	5,222
Current deferred revenue, Less revenue recognized	5,222
Current deferred revenue, ending balance	7,616
Noncurrent deferred revenue, beginning balance	17,942
Noncurrent deferred revenue, Additions	1,785
Noncurrent deferred revenue, Less reclassification to current deferred revenue	1,897
Noncurrent deferred revenue, ending balance	17,830
DJ Basin
Movement in Deferred Revenue [Roll Forward]
Current deferred revenue, beginning balance	739
Current deferred revenue, Additions	393
Current deferred revenue, Less revenue recognized	211
Current deferred revenue, ending balance	921
Noncurrent deferred revenue, beginning balance	7,284
Noncurrent deferred revenue, Additions	1,335
Noncurrent deferred revenue, Less reclassification to current deferred revenue	393
Noncurrent deferred revenue, ending balance	8,226
Barnett Shale
Movement in Deferred Revenue [Roll Forward]
Current deferred revenue, beginning balance	1,642
Current deferred revenue, Additions	409
Current deferred revenue, Less revenue recognized	405
Current deferred revenue, ending balance	1,646
Noncurrent deferred revenue, beginning balance	9,628
Noncurrent deferred revenue, Additions	378
Noncurrent deferred revenue, Less reclassification to current deferred revenue	409
Noncurrent deferred revenue, ending balance	9,597
Marcellus Shale
Movement in Deferred Revenue [Roll Forward]
Current deferred revenue, beginning balance	38
Current deferred revenue, Additions	9
Current deferred revenue, Less revenue recognized	9
Current deferred revenue, ending balance	38
Noncurrent deferred revenue, beginning balance	236
Noncurrent deferred revenue, Additions	0
Noncurrent deferred revenue, Less reclassification to current deferred revenue	9
Noncurrent deferred revenue, ending balance	$ 227