Income Taxes (Expected Income Tax) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Taxes [Abstract]
Expected amount	$ 737	$ 4,868
Adjustment to deferred taxes from the Tax Act rate reduction		(17,974)
State income taxes, net of federal benefit	(654)	115
Percentage depletion	(3,278)	(4,128)
Stock-based compensation	(15)	(204)
Captive insurance		(379)
Adjustments to NOL carryforwards		(1,038)
Return to provision adjustment	(592)	(205)
Other	(273)	(249)
Total tax expected	$ (4,075)	$ (19,194)