DEFERRED REVENUE - Rollforward of deferred revenue (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
Movement in Deferred Revenue [Roll Forward]
Current deferred revenue, beginning balance	$ 4,000
Current deferred revenue, Additions	6,083
Current deferred revenue, Less revenue recognized	6,012
Current deferred revenue, ending balance	10,159
Noncurrent deferred revenue, beginning balance	12,707
Noncurrent deferred revenue, Additions	3,557
Noncurrent deferred revenue, Less reclassification to current deferred revenue	2,498
Noncurrent deferred revenue, ending balance	36,587
Effect of Change Increase / (Decrease)
Movement in Deferred Revenue [Roll Forward]
Current deferred revenue, beginning balance	6,088
Noncurrent deferred revenue, beginning balance	22,821
Adjustment
Movement in Deferred Revenue [Roll Forward]
Current deferred revenue, beginning balance	10,088
Noncurrent deferred revenue, beginning balance	35,528
Utica Shale
Movement in Deferred Revenue [Roll Forward]
Current deferred revenue, beginning balance	0
Current deferred revenue, Additions	5
Current deferred revenue, Less revenue recognized	5
Current deferred revenue, ending balance	18
Noncurrent deferred revenue, beginning balance	0
Noncurrent deferred revenue, Additions	0
Noncurrent deferred revenue, Less reclassification to current deferred revenue	5
Noncurrent deferred revenue, ending balance	34
Utica Shale | Effect of Change Increase / (Decrease)
Movement in Deferred Revenue [Roll Forward]
Current deferred revenue, beginning balance	18
Noncurrent deferred revenue, beginning balance	39
Utica Shale | Adjustment
Movement in Deferred Revenue [Roll Forward]
Current deferred revenue, beginning balance	18
Noncurrent deferred revenue, beginning balance	39
Williston Basin
Movement in Deferred Revenue [Roll Forward]
Current deferred revenue, beginning balance	0
Current deferred revenue, Additions	325
Current deferred revenue, Less revenue recognized	254
Current deferred revenue, ending balance	1,088
Noncurrent deferred revenue, beginning balance	0
Noncurrent deferred revenue, Additions	0
Noncurrent deferred revenue, Less reclassification to current deferred revenue	254
Noncurrent deferred revenue, ending balance	3,961
Williston Basin | Effect of Change Increase / (Decrease)
Movement in Deferred Revenue [Roll Forward]
Current deferred revenue, beginning balance	1,017
Noncurrent deferred revenue, beginning balance	4,215
Williston Basin | Adjustment
Movement in Deferred Revenue [Roll Forward]
Current deferred revenue, beginning balance	1,017
Noncurrent deferred revenue, beginning balance	4,215
Piceance/DJ Basins
Movement in Deferred Revenue [Roll Forward]
Current deferred revenue, beginning balance	4,000
Current deferred revenue, Additions	5,344
Current deferred revenue, Less revenue recognized	5,344
Current deferred revenue, ending balance	7,396
Noncurrent deferred revenue, beginning balance	12,707
Noncurrent deferred revenue, Additions	2,833
Noncurrent deferred revenue, Less reclassification to current deferred revenue	1,830
Noncurrent deferred revenue, ending balance	23,727
Piceance/DJ Basins | Effect of Change Increase / (Decrease)
Movement in Deferred Revenue [Roll Forward]
Current deferred revenue, beginning balance	3,396
Noncurrent deferred revenue, beginning balance	10,017
Piceance/DJ Basins | Adjustment
Movement in Deferred Revenue [Roll Forward]
Current deferred revenue, beginning balance	7,396
Noncurrent deferred revenue, beginning balance	22,724
Barnett Shale
Movement in Deferred Revenue [Roll Forward]
Current deferred revenue, beginning balance	0
Current deferred revenue, Additions	400
Current deferred revenue, Less revenue recognized	400
Current deferred revenue, ending balance	1,619
Noncurrent deferred revenue, beginning balance	0
Noncurrent deferred revenue, Additions	724
Noncurrent deferred revenue, Less reclassification to current deferred revenue	400
Noncurrent deferred revenue, ending balance	8,541
Barnett Shale | Effect of Change Increase / (Decrease)
Movement in Deferred Revenue [Roll Forward]
Current deferred revenue, beginning balance	1,619
Noncurrent deferred revenue, beginning balance	8,217
Barnett Shale | Adjustment
Movement in Deferred Revenue [Roll Forward]
Current deferred revenue, beginning balance	1,619
Noncurrent deferred revenue, beginning balance	8,217
Marcellus Shale
Movement in Deferred Revenue [Roll Forward]
Current deferred revenue, beginning balance	0
Current deferred revenue, Additions	9
Current deferred revenue, Less revenue recognized	9
Current deferred revenue, ending balance	38
Noncurrent deferred revenue, beginning balance	0
Noncurrent deferred revenue, Additions	0
Noncurrent deferred revenue, Less reclassification to current deferred revenue	9
Noncurrent deferred revenue, ending balance	324
Marcellus Shale | Effect of Change Increase / (Decrease)
Movement in Deferred Revenue [Roll Forward]
Current deferred revenue, beginning balance	38
Noncurrent deferred revenue, beginning balance	333
Marcellus Shale | Adjustment
Movement in Deferred Revenue [Roll Forward]
Current deferred revenue, beginning balance	38
Noncurrent deferred revenue, beginning balance	$ 333