Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 31,389	$ 48,138	$ 49,364
Charged to Costs and Expenses	81,180	76,115	88,110
Deductions (1)	(92,092)	(92,864)	(89,336)
Balance at End of Period	20,477	31,389	48,138
Allowance for doubtful accounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	18,325	32,856	36,368
Charged to Costs and Expenses	711	1,235	6,079
Deductions (1)	(8,077)	(15,766)	(9,591)
Balance at End of Period	10,959	18,325	32,856
Reserve for sales returns and allowances
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	4,983	6,121	4,639
Charged to Costs and Expenses	71,865	65,562	72,995
Deductions (1)	(74,107)	(66,700)	(71,513)
Balance at End of Period	2,741	4,983	6,121
Reserve for unapplied rebates
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	8,081	9,161	8,357
Charged to Costs and Expenses	8,604	9,318	9,036
Deductions (1)	(9,908)	(10,398)	(8,232)
Balance at End of Period	$ 6,777	$ 8,081	$ 9,161