Income Taxes - Reconciliation of Income Tax Expense from Statutory Federal Income Tax Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
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	$ 304	$ 1,360	$ 2,912
State income taxes, net of Federal benefit	42	213	452
Oil and mineral depletion	(161)	(213)	(385)
Permanent differences	82	(92)	(172)
Other	69	(143)	(110)
Total provision	$ 336	$ 1,125	$ 2,697