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Fair Value Measurements (Tables)
12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Fair Value Measurements [Abstract]    
Financial Assets And Liabilities Measured At Fair Value On A Recurring Basis
                                 
    Estimated Fair Value at                    
    December 31, 2011     Level 1     Level 2     Level 3  
Corporate bonds (Note 3)   $ 25,709     $ -     $ 25,709     $ -  
Cash equivalents   $ 159,719     $ 159,719     $ -     $ -  
                                 
    Estimated Fair Value at                    
    December 31, 2010     Level 1     Level 2     Level 3  
Corporate bonds (Note 3)   $ 27,866     $ -     $ 27,866     $ -  
Cash equivalents   $ 227,036     $ 227,036     $ -     $ -