Schedule II-Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allowance for Doubtful Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of year	$ 1,255	$ 1,255	$ 1,255
Additions	60	35	189
Deductions	(60)	(35)	(189)
Balance at end of year	1,255	1,255	1,255
Allowance For Sales Returns And Product Warranty [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of year	72,609	62,376	66,221
Additions	109,494	105,987	97,546
Deductions	(110,077)	(95,754)	(101,391)
Balance at end of year	72,026	72,609	62,376
Allowance For Price Protection [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of year	2,125	1,806	4,273
Additions	12,239	7,467	7,534
Deductions	(9,884)	(7,148)	(10,001)
Balance at end of year	$ 4,480	$ 2,125	$ 1,806