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Marketable Securities (Tables)
6 Months Ended
Jun. 30, 2011
Marketable Securities  
Schedule Of Marketable Securities
June 30, 2011   Amortized Cost Basis   Gross Unrealized Holding Gains   Gross Unrealized Holding Losses   Other Than Temporary Impairments   Aggregate Fair Value
                     
Commercial paper    $          4,998   -   -   -    $         4,998
Corporate bonds              15,135                      9                    (1)   -             15,143
Total    $        20,133    $                9    $              (1)   -    $       20,141
                     
                     
December 31, 2010   Amortized Cost Basis   Gross Unrealized Holding Gains   Gross Unrealized Holding Losses   Other Than Temporary Impairments   Aggregate Fair Value
                     
Commercial paper    $        65,244    $              44    $            (27)   -    $       65,261
Corporate bonds              19,186                      6                    (8)   -             19,184
Federal agency obligations              10,003                    12   -   -             10,015

Total

   $        94,433    $              62    $            (35)   -    $       94,460