Accrued Liabilities - Accrued Liabilities Schedule (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Payables and Accruals [Abstract]
Accrued compensation and benefits	$ 16,144	$ 13,649
Accrued warranties	2,628	2,594	$ 2,309	$ 2,719
Professional and legal fees	1,541	1,775
Taxes other than income	3,787	4,026
Other accrued liabilities	3,262	2,528
Total accrued liabilities	$ 27,362	$ 24,572