Schedule II - Valuation and Qualifying Accounts (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Valuation and Qualifying Accounts [Roll Forward]
Balance at beginning of year	$ 5,687,000		$ 4,967,000		$ 4,425,000
Charged to costs and expenses	10,365,000		10,684,000		11,634,000
Other	0		0		0
Deductions	10,840,000		9,964,000		11,092,000
Balance at end of year	5,212,000		5,687,000		4,967,000
Allowance for Doubtful Accounts [Member]
Valuation and Qualifying Accounts [Roll Forward]
Balance at beginning of year	4,488,000		3,824,000		3,353,000
Charged to costs and expenses	(295,000)		325,000		970,000
Other	0		0		0
Deductions	(51,000)		(339,000)		499,000
Balance at end of year	4,244,000		4,488,000		3,824,000
Allowance for Discounts [Member]
Valuation and Qualifying Accounts [Roll Forward]
Balance at beginning of year	1,199,000		1,143,000		1,072,000
Charged to costs and expenses	10,660,000		10,359,000		10,664,000
Other	0		0		0
Deductions	10,891,000		10,303,000		10,593,000
Balance at end of year	968,000		1,199,000		1,143,000
Allowance for Sales Returns [Member]
Valuation and Qualifying Accounts [Roll Forward]
Balance at beginning of year	57,433,000		35,916,000		40,176,000
Charged to costs and expenses	136,777,000		132,390,000		137,416,000
Other	0	[1]	6,670,000	[1]	0
Deductions	150,094,000		117,543,000		141,676,000
Balance at end of year	$ 44,116,000		$ 57,433,000		$ 35,916,000

[1] The other addition to the allowance for sales returns represents the cumulative effect of the changes made to our consolidated balance sheet as of January 1, 2018 for the adoption of ASU 2014-09, Revenue from Contracts with Customers.