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Summary of Significant Accounting Policies - Fair Value Measurements (Details) (USD $)
Mar. 31, 2013
Dec. 31, 2012
Assets Measured on Recurring Basis    
Available-for-sale Securities, Fair Value Disclosure $ 48,408,220  
Assets, Fair Value Disclosure 84,052,145 98,024,269
Fair Value, Assets, Level 1 to Level 2 Transfers, Amount 0 0
Level 1
   
Assets Measured on Recurring Basis    
Assets, Fair Value Disclosure 35,643,925 98,024,269
Level 2
   
Assets Measured on Recurring Basis    
Assets, Fair Value Disclosure 48,408,220 0
Cash Equivalents
   
Assets Measured on Recurring Basis    
Cash and Cash Equivalents, Fair Value Disclosure 35,643,925 98,024,269
Cash Equivalents | Level 1
   
Assets Measured on Recurring Basis    
Cash and Cash Equivalents, Fair Value Disclosure 35,643,925 98,024,269
Corporate Debt Securities
   
Assets Measured on Recurring Basis    
Available-for-sale Securities, Fair Value Disclosure 39,426,922 0
Corporate Debt Securities | Level 2
   
Assets Measured on Recurring Basis    
Available-for-sale Securities, Fair Value Disclosure 39,426,922 0
Commercial Paper
   
Assets Measured on Recurring Basis    
Available-for-sale Securities, Fair Value Disclosure 5,981,298 0
Commercial Paper | Level 2
   
Assets Measured on Recurring Basis    
Available-for-sale Securities, Fair Value Disclosure 5,981,298 0
Certificate of Deposit
   
Assets Measured on Recurring Basis    
Available-for-sale Securities, Fair Value Disclosure 3,000,000 0
Certificate of Deposit | Level 2
   
Assets Measured on Recurring Basis    
Available-for-sale Securities, Fair Value Disclosure 3,000,000 0
Investments | Level 3
   
Assets Measured on Recurring Basis    
Investments, Fair Value Disclosure $ 0 $ 0