Valuation and Qualifying accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Allowance for Doubtful Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation Allowances and Reserves, Opening Balance	$ 57	$ 353	$ 430
Valuation Allowances and Reserves, Charged to Cost and Expense	(19)	(46)	55
Valuation Allowances and Reserves, Adjustments	7	250	132
Valuation Allowances and Reserves, Closing Balance	31	57	353
Allowance for Sales Returns [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation Allowances and Reserves, Opening Balance	401	530	429
Valuation Allowances and Reserves, Charged to Cost and Expense	3,442	3,729	5,375
Valuation Allowances and Reserves, Adjustments	3,353	3,858	5,274
Valuation Allowances and Reserves, Closing Balance	$ 490	$ 401	$ 530