Schedule II - Valuation And Qualifying Accounts (Schedule Of Valuation And Qualifying Accounts) (Details) (Allowance For Doubtful Accounts [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Allowance For Doubtful Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 9,484	$ 9,167	$ 9,555
Charged to Costs and Expenses	633	1,047	899
Write-off of Doubtful Accounts	(37)	730	1,287
Balance at End of Period	$ 10,154	$ 9,484	$ 9,167