Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Allowance for doubtful accounts
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 7,219	$ 4,086	$ 4,842	$ 3,270
Additions charged to Expense or Revenue	150	800	2,600	1,635
Deductions and write-offs	(409)	(536)	(482)	(555)
Balance at End of Period	6,960	4,350	6,960	4,350
Allowance for sales returns, discounts and allowances
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	3,461	2,191	4,894	1,262
Additions charged to Expense or Revenue	1,288	2,591	5,794	5,917
Deductions and write-offs	(1,270)	(2,520)	(7,209)	(4,917)
Balance at End of Period	3,479	2,262	3,479	2,262
Allowance for obsolescence
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	1,113	1,780	828	397
Additions charged to Expense or Revenue	212	339	953	1,910
Deductions and write-offs	(336)	(1,411)	(792)	(1,599)
Balance at End of Period	$ 989	$ 708	$ 989	$ 708