Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Natural gas sales	$ 3,523	$ 4,023	$ 7,462	$ 8,017
Natural gas liquids sales	550		713
Oil sales	8,091	$ 1,146	11,074	$ 2,192
Total revenue	12,164		19,249
Appalachia and Illinois Basin [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Natural gas sales	3,114		6,919
Natural gas liquids sales
Oil sales	2,377		2,624
Total revenue	5,491		9,543
Ventura Basin [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Natural gas sales	409		543
Natural gas liquids sales	550		713
Oil sales	5,714		8,450
Total revenue	$ 6,673		$ 9,706