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Fair Value Of Financial Instruments (Details2) (USD $)
In Thousands, unless otherwise specified
Jun. 30, 2012
Dec. 31, 2011
Fair Value
   
Fair value hierarchy for its financial assets    
Money market funds $ 790 $ 2,792
Total assets 48,409 20,742
Fair Value | Certificates of deposit
   
Fair value hierarchy for its financial assets    
Available-for-sale securities 4,790  
Fair Value | Corporate notes and commercial paper
   
Fair value hierarchy for its financial assets    
Available-for-sale securities 22,912  
Fair Value | Corporate notes
   
Fair value hierarchy for its financial assets    
Available-for-sale securities   7,393
Fair Value | U.S. government debt securities
   
Fair value hierarchy for its financial assets    
Available-for-sale securities 19,917 10,557
Level 1
   
Fair value hierarchy for its financial assets    
Money market funds 790 2,792
Total assets 790 2,792
Level 2
   
Fair value hierarchy for its financial assets    
Total assets 47,619 17,950
Level 2 | Certificates of deposit
   
Fair value hierarchy for its financial assets    
Available-for-sale securities 4,790  
Level 2 | Corporate notes and commercial paper
   
Fair value hierarchy for its financial assets    
Available-for-sale securities 22,912  
Level 2 | Corporate notes
   
Fair value hierarchy for its financial assets    
Available-for-sale securities   7,393
Level 2 | U.S. government debt securities
   
Fair value hierarchy for its financial assets    
Available-for-sale securities $ 19,917 $ 10,557