Related Party Transactions (Schedule of Related Party Disclosures) (Details) - Majority Shareholder - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Total Services from CONSOL Energy	$ 11,218	$ 6,612	$ 8,077
Operating and Other Costs
Related Party Transaction [Line Items]
Total Services from CONSOL Energy	2,918	3,503	4,251
Selling, General and Administrative Costs
Related Party Transaction [Line Items]
Total Services from CONSOL Energy	$ 8,300	$ 3,109	$ 3,826