Valuation And Qualifying Accounts (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Valuation and Qualifying Accounts [Abstract]
Valuation Allowances and Reserves, Balance at Beginning of Year	$ 12,559		$ 8,092		$ 7,859
Valuation Allowances and Reserves, Charged as Reduction Revenue	12,872	[1]	12,960	[1]	14,060	[1]
Valuation allowances and reserves, Charge in Deferred Revenue	(611)	[1]	516	[1]	(50)	[1]
Valuation Allowances and Reserves, Deductions	(9,661)	[2]	(9,009)	[2]	(13,777)	[2]
Valuation Allowances and Reserves, Balance at End of Year	$ 15,159		$ 12,559		$ 8,092

[1] Additions to sales discounts and allowances are recorded as a reduction of deferred revenue until such time revenue is recognized.

[2] Deductions to sales discounts and allowances relate to discounts or allowances actually taken or paid.