Quarterly report pursuant to Section 13 or 15(d)

Related-Party Transactions - Additional Information (Details)

v3.19.1
Related-Party Transactions - Additional Information (Details)
3 Months Ended
Mar. 31, 2019
USD ($)
Mar. 31, 2018
USD ($)
Dec. 31, 2018
USD ($)
Sep. 30, 2018
Director
Related Party Transaction [Line Items]        
Receivable from agreement $ 3,338,000   $ 2,489,000  
Celgene        
Related Party Transaction [Line Items]        
Number of directors performed consulting services | Director       3
Payments for performed consulting services 0      
Celgene | Director One        
Related Party Transaction [Line Items]        
Payments for performed consulting services   $ 15,000    
Celgene | Director Two        
Related Party Transaction [Line Items]        
Payments for performed consulting services   7,500    
Celgene | Director Three        
Related Party Transaction [Line Items]        
Payments for performed consulting services   $ 7,500    
SutroVax        
Related Party Transaction [Line Items]        
Receivable from agreement $ 300,000   $ 49,000  
Percentage common stock ownership interest 5.60% 5.60%    
Carrying value of common stock under the cost method $ 0 $ 0    
Sutro Biopharma | Celgene | Maximum [Member] | IPO        
Related Party Transaction [Line Items]        
Equity interest percentage 10.00%      
Sutro Biopharma | Merck        
Related Party Transaction [Line Items]        
Equity interest percentage 11.90%   11.90%