Quarterly report pursuant to Section 13 or 15(d)

Document and Entity Information

Document and Entity Information - shares
9 Months Ended
Sep. 30, 2020
Oct. 30, 2020
Cover [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Sep. 30, 2020  
Document Fiscal Year Focus 2020  
Document Fiscal Period Focus Q3  
Trading Symbol STRO  
Entity Registrant Name SUTRO BIOPHARMA, INC.  
Entity Central Index Key 0001382101  
Current Fiscal Year End Date --12-31  
Entity Filer Category Accelerated Filer  
Entity Small Business true  
Entity Emerging Growth Company true  
Entity Ex Transition Period false  
Entity Current Reporting Status Yes  
Entity Shell Company false  
Entity File Number 001-38662  
Entity Tax Identification Number 47-0926186  
Entity Address, Address Line One 310 Utah Avenue  
Entity Address, Address Line Two Suite 150  
Entity Address, City or Town South San Francisco  
Entity Address, State or Province CA  
Entity Address, Postal Zip Code 94080  
City Area Code 650  
Local Phone Number 392-8412  
Entity Common Stock, Shares Outstanding   38,604,176
Security Exchange Name NASDAQ  
Title of 12(b) Security Common stock, $0.001 par value  
Document Quarterly Report true  
Document Transition Report false  
Entity Incorporation, State or Country Code DE  
Entity Interactive Data Current Yes