Schedule II - Valuation and Qualifying Accounts (Valuation and Qualifying Accounts) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Allowance for Sales Returns [Member]
Balance at beginning of period	$ 6,406		$ 5,634		$ 5,316
Additions - charged to costs and expenses	920		772		318
Additions - charged to other accounts - describe	0		0		0
Deductions - describe	0		0		0
Balance at end of period	7,326		6,406		5,634
Allowance for Doubtful Accounts [Member]
Balance at beginning of period	6,403		8,349		6,795
Additions - charged to costs and expenses	8,043		7,695		9,250
Additions - charged to other accounts - describe	0		0		0
Deductions - describe	7,999	[1]	9,641	[1]	7,696	[1]
Balance at end of period	$ 6,447		$ 6,403		$ 8,349

[1] Uncollectable accounts written off.