Schedule II - Schedule of Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for doubtful accounts and returns
Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	$ 236	$ 155	$ 307
Charges to Revenue/ Expense	23	156	39
Deductions	217	75	191
Ending Balance	42	236	155
Reserve for excess, obsolete, and slow moving inventories
Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	5,596	2,315	576
Charges to Revenue/ Expense	1,139	6,110	2,066
Deductions	2,539	2,829	327
Ending Balance	4,196	5,596	2,315
Valuation allowance for deferred tax assets
Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	12,537	7,768	9,008
Charges to Revenue/ Expense	3,883	4,769	(1,240)
Deductions	5,864	0	0
Ending Balance	$ 10,556	$ 12,537	$ 7,768