SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Allowance for doubtful accounts
Schedule of Valuation and Qualifying Accounts [Roll Forward]
Balance at Beginning of Year	$ 463	$ 261
Additions Charged to Costs and Expenses	351	562
Additions Charged to other Accounts	0	0
Deductions	(232)	(360)
Balance at End of Year	582	463
Allowance for obsolete inventories
Schedule of Valuation and Qualifying Accounts [Roll Forward]
Balance at Beginning of Year	381	1,265
Additions Charged to Costs and Expenses	714	343
Additions Charged to other Accounts	0	0
Deductions	(529)	(1,227)
Balance at End of Year	566	381
Valuation allowance for deferred tax assets
Schedule of Valuation and Qualifying Accounts [Roll Forward]
Balance at Beginning of Year	8,458	9,028
Additions Charged to Costs and Expenses	3,549	463
Additions Charged to other Accounts	0	0
Deductions	(571)	(1,033)
Balance at End of Year	11,436	8,458
Reserve for sales returns
Schedule of Valuation and Qualifying Accounts [Roll Forward]
Balance at Beginning of Year	129	147
Additions Charged to Costs and Expenses	1,277	1,334
Additions Charged to other Accounts	0	0
Deductions	(1,289)	(1,352)
Balance at End of Year	$ 117	$ 129