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Fair Value Measurements (Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) (USD $)
In Thousands, unless otherwise specified
3 Months Ended 12 Months Ended
Mar. 31, 2012
Dec. 31, 2011
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]    
Treasury lock $ 36,500  
Cash And Cash Equivalents [Member]
   
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]    
Cash 499 499
Money market funds 83,518 155,814
Cash And Cash Equivalents [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
   
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]    
Cash 499 499
Money market funds 83,518 155,814
Accrued Liabilities [Member]
   
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]    
Treasury lock 36,538 48,829
Accrued Liabilities [Member] | Other Observable Inputs (Level 2) [Member]
   
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]    
Treasury lock $ 36,538 $ 48,829