REVENUE FROM CONTRACTS WITH CUSTOMERS - Concentrations (Details) - Customer Concentration Risk - Revenue Benchmark	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Vitol Midstream
Concentration Risk [Line Items]
Concentration risk, percentage	26.00%	15.00%
Shell Trading US Company
Concentration Risk [Line Items]
Concentration risk, percentage	22.00%	27.00%	26.00%
Plains Marketing LP
Concentration Risk [Line Items]
Concentration risk, percentage	20.00%	23.00%
Trafigura Trading LLC
Concentration Risk [Line Items]
Concentration risk, percentage	11.00%
Koch Supply & Trading LP
Concentration Risk [Line Items]
Concentration risk, percentage			15.00%
Occidental Energy Marketing Inc.
Concentration Risk [Line Items]
Concentration risk, percentage			11.00%