Collaborations and License Agreements - Additional Information (Detail) (USD $)
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]    
Research and development $ 23,027,578 $ 15,486,476
Licensing Agreements [Member]
   
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]    
License expiration period On the later of 10 years after the first commercial sale of a product developed using the licensed compound or upon expiration of the patent rights  
Royalty payments 0 0
Takeda Pharmaceutical Company Limited [Member] | Collaborative Arrangement [Member]
   
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]    
R&D services revenue recognition period 3 years  
Recognized revenue 2,700,000 3,100,000
Deferred revenue 0 1,700,000
Takeda Pharmaceutical Company Limited [Member] | Maximum [Member] | Development Milestones [Member]
   
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]    
Aggregate payment upon achievement of certain milestones 500,000,000  
Takeda Pharmaceutical Company Limited [Member] | Maximum [Member] | Sales-Based Milestones [Member]
   
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]    
Aggregate payment upon achievement of certain milestones 250,000,000  
University [Member] | Licensing Agreements [Member]
   
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]    
License expiration period Upon expiration of the patent rights or 15 years subsequent to the first sale of products developed through this License.  
Number of common stock issued 400,000  
Research and development 120,000  
Other payments 0 0
University [Member] | Minimum [Member] | Licensing Agreements [Member]
   
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]    
Annual spending requirements for development and commercialization of technology expense $ 1,000,000