SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allowance for Sales Returns
Valuation and Qualifying Accounts
Beginning Balance	$ 3,235	$ 3,223	$ 3,060
Charged to Costs and Expenses	32,909	30,289	32,882
Deductions/Write-Offs	(32,435)	(30,277)	(32,719)
Ending Balance	3,709	3,235	3,223
Allowance for Doubtful Accounts
Valuation and Qualifying Accounts
Beginning Balance	2,219	2,135	2,265
Charged to Costs and Expenses	360	1,097	1,383
Deductions/Write-Offs	(269)	(1,013)	(1,513)
Ending Balance	$ 2,310	$ 2,219	$ 2,135