Income Taxes (Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Income Taxes [Abstract]
Stock-based compensation	$ 613	$ 251
Investment		781
Net operating loss	17,194	13,626
Interest limitation carryforward	441
Alternative minimum tax credit	1,049	2,705
Other	995	943
Total long-term deferred tax assets	20,292	18,306
Coal properties	(46,733)	(47,034)
Net deferred tax liability	$ (26,441)	$ (28,728)