Quarterly report pursuant to Section 13 or 15(d)

Organization and Summary of Significant Accounting Policies - Additional Information (Detail)

v3.8.0.1
Organization and Summary of Significant Accounting Policies - Additional Information (Detail)
3 Months Ended 9 Months Ended
Aug. 01, 2017
Sep. 30, 2017
USD ($)
Sep. 30, 2016
USD ($)
Sep. 30, 2017
USD ($)
Sep. 30, 2016
USD ($)
Dec. 31, 2016
USD ($)
Organization And Summary Of Significant Accounting Policies [Line Items]            
Reverse stock split of common stock, description       11-for-1 reverse stock split    
Reverse stock split of common stock conversion ratio 11          
Grant revenue   $ 0 $ 0 $ 167,000 $ 1,526,000  
Accounts receivable   0   0    
Accounts receivable   $ 38,000   $ 38,000   $ 0
Takeda Pharmaceuticals Inc            
Organization And Summary Of Significant Accounting Policies [Line Items]            
Accounts receivable           $ 0
Revenue | Credit Risk            
Organization And Summary Of Significant Accounting Policies [Line Items]            
Percentage of total revenues   100.00%   74.00%