Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
VAT receivable	$ 14,088	$ 9,306
Prepaid income tax asset	2,314	1,910
Other	2,282	2,831
Total other current assets	$ 18,684	$ 14,047