RELATED PARTY TRANSACTIONS - Schedule of Related Party Disclosures (Details) - Majority Shareholder - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Related Party Transaction [Line Items]
Total Services from CONSOL Energy	$ 2,740	$ 3,070	$ 9,300	$ 8,115
Operating and Other Costs
Related Party Transaction [Line Items]
Total Services from CONSOL Energy	838	725	2,368	2,172
Selling, General and Administrative Costs
Related Party Transaction [Line Items]
Total Services from CONSOL Energy	$ 1,902	$ 2,345	$ 6,932	$ 5,943