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Financial Instruments (Details) (USD $)
Jun. 30, 2012
Dec. 31, 2011
Available-for-sale marketable securities    
Amortized Cost $ 8,903,314 $ 16,594,470
Gross Unrealized Gains      
Gross Unrealized (Losses) (71) (2,618)
Fair Value 8,903,243 16,591,852
Cash [Member]
   
Available-for-sale marketable securities    
Amortized Cost 192,843 291,093
Gross Unrealized Gains      
Fair Value 192,843 291,093
Cash equivalents [Member]
   
Available-for-sale marketable securities    
Amortized Cost 7,010,586 13,020,168
Gross Unrealized Gains      
Fair Value 7,010,586 13,020,168
Marketable debt securities, current [Member]
   
Available-for-sale marketable securities    
Amortized Cost 1,699,885 3,283,209
Gross Unrealized Gains      
Gross Unrealized (Losses) (71) (2,618)
Fair Value $ 1,699,814 $ 3,280,591