Schedule II - Schedule of Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Allowance for doubtful accounts and returns
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	$ 42	$ 236	$ 155
Charges to Revenue/ Expense	20	23	156
Deductions	29	217	75
Ending Balance	33	42	236
Reserve for excess, obsolete, and slow moving inventories
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	4,196	5,596	2,315
Charges to Revenue/ Expense	1,085	1,139	6,110
Deductions	1,069	2,539	2,829
Ending Balance	4,212	4,196	5,596
Valuation allowance for deferred tax assets
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	10,556	12,537	7,768
Charges to Revenue/ Expense	2,187	3,883	4,769
Deductions	0	5,864	0
Ending Balance	$ 12,743	$ 10,556	$ 12,537