Annual report pursuant to Section 13 and 15(d)

Document and Entity Information

Document and Entity Information - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2020
Mar. 11, 2021
Jun. 30, 2020
Cover [Abstract]      
Document Type 10-K    
Amendment Flag false    
Document Period End Date Dec. 31, 2020    
Document Fiscal Year Focus 2020    
Document Fiscal Period Focus FY    
Trading Symbol STRO    
Entity Registrant Name SUTRO BIOPHARMA, INC.    
Entity Central Index Key 0001382101    
Current Fiscal Year End Date --12-31    
Entity Filer Category Non-accelerated Filer    
Entity Well-known Seasoned Issuer Yes    
Entity Current Reporting Status Yes    
Entity Voluntary Filers No    
Entity Small Business true    
Entity Emerging Growth Company true    
Entity Ex Transition Period false    
ICFR Auditor Attestation Flag false    
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   45,892,331  
Security Exchange Name NASDAQ    
Title of 12(b) Security Common stock, $0.001 par value    
Document Annual Report true    
Document Transition Report false    
Entity Incorporation, State or Country Code DE    
Entity Interactive Data Current Yes    
Entity Public Float     $ 261.1
Documents Incorporated by Reference Portions of the registrant’s definitive proxy statement to be filed for its 2021 Annual Meeting of Stockholders are incorporated by reference into Part III hereof. Such proxy statement will be filed with the Securities and Exchange Commission within 120 days of the end of the fiscal year covered by this Annual Report on Form 10-K.