Annual report pursuant to Section 13 and 15(d)

Related-Party Transactions - Additional Information (Details)

v3.19.1
Related-Party Transactions - Additional Information (Details)
 12 Months Ended 84 Months Ended
Jul. 31, 2018
USD ($)
Jun. 30, 2018
USD ($)
May 31, 2018
USD ($)
shares
Aug. 30, 2010
USD ($)
Dec. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Dec. 31, 2015
$ / shares
shares
Sep. 30, 2018
Director
Related Party Transaction [Line Items]                  
Principal amount of promissory notes           $ 208,000      
Accounts receivable         $ 2,489,000 1,624,000      
Remaining deliverables under license agreement         0        
Second Director Performing Consulting Services                  
Related Party Transaction [Line Items]                  
Payments for performed consulting services         20,000 30,000 $ 30,000    
Options granted to purchase common stock | shares               3,269  
Third Director Performing Consulting Services                  
Related Party Transaction [Line Items]                  
Payments for performed consulting services         20,000 25,000 0    
Chief Executive Officer                  
Related Party Transaction [Line Items]                  
Principal amount of promissory notes       $ 200,000          
Promissory note, accrued interest rate percentage       0.53%          
Promissory note maturity date       Aug. 30, 2019          
Collaboration Agreements                  
Related Party Transaction [Line Items]                  
Related party transaction agreed to pay one time success fee   $ 400,000              
Merck Agreement                  
Related Party Transaction [Line Items]                  
Execution of directors fees paid $ 400,000                
Celgene                  
Related Party Transaction [Line Items]                  
Number of directors performed consulting services | Director                 3
Celgene | First Director Performing Consulting Service                  
Related Party Transaction [Line Items]                  
Payments for performed consulting services         40,000 60,000 60,000    
Options granted to purchase common stock | shares               9,805  
Advisory fees         200,000 500,000 $ 700,000    
SutroVax                  
Related Party Transaction [Line Items]                  
Accounts receivable         $ 49,000 $ 34,000      
Percentage common stock ownership interest         5.60% 7.80%      
Carrying value of common stock under the cost method         $ 0        
Number of warrants to purchase | shares     100,000            
Value of warrant to purchase of preferred stock     $ 100,000            
Maximum | Celgene | First Director Performing Consulting Service                  
Related Party Transaction [Line Items]                  
Fair values of the common stock price per share | $ / shares               $ 11.98  
Minimum | Second Director Performing Consulting Services                  
Related Party Transaction [Line Items]                  
Fair values of the common stock price per share               4 years  
Minimum | Celgene | First Director Performing Consulting Service                  
Related Party Transaction [Line Items]                  
Fair values of the common stock price per share | $ / shares               $ 4.36  
Fair values of the common stock price per share               4 years  
Sutro Biopharma | Celgene                  
Related Party Transaction [Line Items]                  
Equity interest percentage           15.40%      
Sutro Biopharma | Merck                  
Related Party Transaction [Line Items]                  
Equity interest percentage         11.90% 0.00%      
Sutro Biopharma | Maximum | Celgene                  
Related Party Transaction [Line Items]                  
Equity interest percentage         10.00%