Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Accrued payroll	$ 4,647	$ 6,201
Product warranty, current	3,495	3,589
Income tax payable	1,341	931
Other accrued expenses	2,387	1,929
Total accrued liabilities	$ 11,870	$ 12,650