Document and Entity Information - shares
9 Months Ended
Sep. 30, 2019
Nov. 07, 2019
Cover [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Sep. 30, 2019  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q3  
Trading Symbol SURF  
Entity Registrant Name SURFACE ONCOLOGY, INC.  
Entity Central Index Key 0001718108  
Current Fiscal Year End Date --12-31  
Entity Filer Category Non-accelerated Filer  
Entity Small Business true  
Entity Emerging Growth Company true  
Entity Ex Transition Period true  
Entity Current Reporting Status Yes  
Entity Shell Company false  
Entity File Number 001-38459  
Entity Tax Identification Number 46-5543980  
Entity Address, Address Line One 50 Hampshire Street  
Entity Address, Address Line Two 8th Floor  
Entity Address, City or Town Cambridge  
Entity Address, State or Province MA  
Entity Address, Postal Zip Code 02139  
City Area Code 617  
Local Phone Number 714-4096  
Entity Common Stock, Shares Outstanding   27,882,756
Entity Interactive Data Current Yes  
Title of 12(b) Security Common stock, $0.0001  
Security Exchange Name NASDAQ  
Entity Incorporation, State or Country Code DE  
Document Quarterly Report true  
Document Transition Report false