Schedule II Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Deferred tax valuation allowance
Valuation and Qualifying Accounts
Balance at Beginning of Year	$ 3,071	$ 1,000	$ 0
Charged to Expense	1,168	2,071	1,000
Deductions	0	0	0
Balance at End of Year	4,239	3,071	1,000
Allowance for sales returns
Valuation and Qualifying Accounts
Balance at Beginning of Year	17,896	15,531	13,232
Charged to Expense	163,693	142,887	117,932
Deductions	163,413	140,522	115,633
Balance at End of Year	18,176	17,896	15,531
Allowance for doubtful accounts
Valuation and Qualifying Accounts
Balance at Beginning of Year	465	511	152
Charged to Expense	1,608	217	359
Deductions	74	263	0
Balance at End of Year	$ 1,999	$ 465	$ 511