Income Taxes - Reconciliation of Income Tax Expense from Statutory Federal Income Tax Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Federal statutory tax rate	34.00%	34.00%	34.00%
Difference between total income tax expense and the amount computed by applying the statutory Federal income tax rate to income before taxes:
Income tax at statutory rate	$ (910)	$ 304	$ 1,360
State income taxes, net of Federal benefit	(161)	42	213
Oil and mineral depletion	(180)	(161)	(213)
Permanent differences	25	82	(92)
Excess stock compensation expense	107	0	0
Tax Reform adjustment	54	0	0
Other	(58)	69	(143)
(Benefit) provision for income taxes	$ (1,123)	$ 336	$ 1,125
Effective tax rate	42.00%	37.60%	28.10%