Valuation and Qualifying accounts (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Allowance for Doubtful Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Valuation Allowances and Reserves, Opening Balance	$ 430	$ 390	$ 361
Valuation Allowances and Reserves, Charged to Cost and Expense	55	48	30
Valuation Allowances and Reserves, Adjustments	132	8	1
Valuation Allowances and Reserves, Closing Balance	353	430	390
Allowance for Sales Returns [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Valuation Allowances and Reserves, Opening Balance	429	1,411	584
Valuation Allowances and Reserves, Charged to Cost and Expense	5,375	4,265	6,750
Valuation Allowances and Reserves, Adjustments	5,274	5,247	5,923
Valuation Allowances and Reserves, Closing Balance	$ 530	$ 429	$ 1,411