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Fair Value Measurements (Tables)
6 Months Ended 12 Months Ended
Jun. 30, 2011
Dec. 31, 2010
Fair Value Measurements    
Financial Assets And Liabilities Measured At Fair Value On A Recurring Basis
                                 
   
Estimated Fair Value
at
                   
   
June 30, 2011
   
Level 1
   
Level 2
   
Level 3
 
Securities issued by government agencies (Note 3)
  $ 5,003     $ -     $ 5,003     $ -  
Corporate bonds (Note 3)
    33,649       -       33,649       -  
Available for sale marketable debt securities
  $ 38,652     $ -     $ 38,652     $ -  
                                 
   
Estimated Fair Value
at
                   
   
December 31, 2010
   
Level 1
   
Level 2
   
Level 3
 
Corporate bonds (Note 3)
  $ 27,866     $ -     $ 27,866     $ -