Document and Entity Information - shares
6 Months Ended
Jun. 30, 2019
Aug. 05, 2019
Document And Entity Information [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Jun. 30, 2019  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q2  
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 465543980  
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   27,858,000