Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Accrued payroll	$ 11,649	$ 11,693
Accrued rent	1,198	1,180
Accrued employee benefits	2,236	2,035
Accrued state and local taxes	792	951
Advance payments	320	441
Accrued product warranty	1,218	1,118
Accrued commission expenses	209	425
Accrued professional fees	443	181
Accrued capital expenditures	1,131
Accrued other	1,527	1,079
Total accrued liabilities	$ 20,723	$ 19,103