Recently Issued Accounting Standards (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue receivable	$ 7,860		$ 7,860		$ 15,340
Revenue	21,561	$ 24,251	46,478	$ 45,023
Oil production
Disaggregation of Revenue [Line Items]
Revenue receivable	2,400		2,400
Revenue	5,660	7,300	11,982	14,171
Natural gas production
Disaggregation of Revenue [Line Items]
Revenue receivable	4,100		4,100
Revenue	11,825	13,751	26,709	24,413
Natural gas liquids production
Disaggregation of Revenue [Line Items]
Revenue receivable	1,400		1,400
Revenue	$ 4,076	$ 3,200	$ 7,788	$ 6,439
Minimum
Disaggregation of Revenue [Line Items]
Revenue recognized, period			1 month
Maximum
Disaggregation of Revenue [Line Items]
Revenue recognized, period			2 months