Other Long-Term Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Restricted Cash and Cash Equivalents Items [Line Items]
Cash surrender value of corporate-owned life insurance policies	$ 3,846	$ 3,240
Deferred commissions	6,803	5,302
Restricted cash	3,333	3,317
Prepaid expenses, deposits and other	1,384	2,058
Total other long-term assets	15,366	$ 13,917
Open purchase order	51,900
Customer A
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	2,700
Customer B
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	$ 600