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Valuation And Qualifying Accounts (Details) (Allowance For Doubtful Accounts [Member], USD $)
 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 - Beginning of Period $ 4,069,000 $ 4,640,000 $ 3,214,000
Additions Charged to Costs and Expenses 2,450,000 2,200,000 2,404,000
Additions Charged to Other Accounts         
Deductions 2,013,000 [1] 2,771,000 [1] 978,000 [1]
Balance - End Of Period $ 4,506,000 $ 4,069,000 $ 4,640,000
[1] Represents write-offs