Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Excise and other taxes receivable	$ 4,910	$ 3,860
Material and chemical inventories	961	1,252
Exchange and other receivables	532	831
Other current assets	$ 6,403	$ 5,943