Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Valuation and Qualifying Accounts [Roll Forward]
Balance Beginning of Year	$ 2,756	$ 1,678	$ 1,467
Charged to Costs and Expenses	7,265	7,409	6,652
Write-offs, Net of Recoveries and Actual Returns	(7,353)	(6,331)	(6,441)
Balance at End of Year	2,668	2,756	1,678
Allowance for doubtful accounts
Valuation and Qualifying Accounts [Roll Forward]
Balance Beginning of Year	1,821	936	898
Charged to Costs and Expenses	1,764	1,422	446
Write-offs, Net of Recoveries and Actual Returns	(1,941)	(537)	(408)
Balance at End of Year	1,644	1,821	936
Allowance for returns
Valuation and Qualifying Accounts [Roll Forward]
Balance Beginning of Year	935	742	569
Charged to Costs and Expenses	5,501	5,987	6,206
Write-offs, Net of Recoveries and Actual Returns	(5,412)	(5,794)	(6,033)
Balance at End of Year	$ 1,024	$ 935	$ 742