Income Taxes (Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred income tax assets
Bad debts	$ 2	$ 3
Stock-based compensation	1,344	3,050
Accrued liabilities and other	29	49
Deferred revenue	180	413
Net operating losses	29,274	31,130
Total net deferred tax assets	30,829	34,645
Deferred income tax liabilities
Prepaids	(210)	(378)
Property, plant and equipment	(18,906)	(20,890)
Total net deferred tax liabilities	(19,116)	(21,268)
Valuation allowance	(12,396)	(13,773)
Net deferred tax liability	$ (683)	$ (396)