Accrued Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Accrued payroll	$ 9,503	$ 11,693
Accrued rent	1,190	1,180
Accrued employee benefits	2,020	2,035
Accrued state and local taxes	454	951
Advance payments	464	441
Accrued product warranty	1,324	1,118
Accrued commission expenses	295	425
Accrued professional fees	201	181
Accrued other	1,200	1,079
Total accrued liabilities	$ 16,651	$ 19,103