Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Revenue from contract with customers (Details)

v3.8.0.1
Summary of Significant Accounting Policies - Revenue from contract with customers (Details)
1 Months Ended 3 Months Ended 47 Months Ended
Sep. 30, 2017
USD ($)
Jun. 30, 2014
USD ($)
Mar. 31, 2018
USD ($)
contract
Mar. 31, 2018
USD ($)
Mar. 31, 2017
USD ($)
Mar. 31, 2018
USD ($)
Collaboration and License Agreement            
Option exercise fee     $ 8,196,000 $ 8,196,000 $ 2,857,000  
GlaxoSmithKline Intellectual Property Development Ltd | Collaboration and License Agreement            
Collaboration and License Agreement            
Number of contracts with customers | contract     1      
Upfront payment received   $ 42,123,000        
Amount of development milestone achieved           $ 53,433,000
Estimate of variable consideration     $ 20,039,000      
License exercise fee, expected to be received     $ 14,032,000      
Licenses | GlaxoSmithKline Intellectual Property Development Ltd | Collaboration and License Agreement            
Collaboration and License Agreement            
Option exercise fee $ 26,610,000