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Significant Accounting Policies - Additional Information (Details) - USD ($)
3 Months Ended 6 Months Ended
Dec. 12, 2013
Jun. 30, 2015
Jun. 30, 2014
Jun. 30, 2015
Jun. 30, 2014
Feb. 28, 2015
Schedule Of Significant Accounting Policies [Line Items]            
Expenses related to patents $ 30,000 $ 253,967 $ (7,575) $ 339,345 $ 152,969  
Amgen Inc.            
Schedule Of Significant Accounting Policies [Line Items]            
Upfront payment received   54,100,000   54,100,000   $ 60,000,000
Deferred revenue recognized   4,400,000   7,300,000    
Certificates of Deposit            
Schedule Of Significant Accounting Policies [Line Items]            
Long-term restricted cash   $ 1,500,000   $ 1,500,000