Income Taxes (Details 2) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets
Net operating loss carryforwards	$ 8,066	$ 6,407
Depletion carryforwards	2,185	1,934
Accrual and other	863	450
Stock-based compensation	449	476
Asset retirement obligations	4,640	1,944
Property, plant and equipment	2,340	2,972
Total deferred tax assets	18,543	14,183
Deferred tax liability
Interest in partnerships	(517)	(790)
Derivative and other	(1,056)	(57)
Less valuation allowance	(16,970)	(13,336)
Net deferred tax asset