SEGMENT INFORMATION - Concentration Risk (Details) - Revenue - Customer concentration	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Counterparty A - Piceance/DJ Basins
Segment Reporting Information [Line Items]
Concentration risk, percentage	10.00%	0.00%	11.00%	0.00%
Counterparty B - Piceance/DJ Basins
Segment Reporting Information [Line Items]
Concentration risk, percentage	0.00%	10.00%	0.00%	0.00%
Counterparty C - Barnett Shale
Segment Reporting Information [Line Items]
Concentration risk, percentage	11.00%	11.00%	0.00%	0.00%
Counterparty D - Utica Shale
Segment Reporting Information [Line Items]
Concentration risk, percentage	0.00%	10.00%	0.00%	0.00%
Counterparty E - Williston Basin
Segment Reporting Information [Line Items]
Concentration risk, percentage	0.00%	0.00%	0.00%	21.00%