Document and Entity Information
6 Months Ended
Jun. 30, 2015
Aug. 07, 2015
Document And Entity Information [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Jun. 30, 2015  
Document Fiscal Year Focus 2015  
Document Fiscal Period Focus Q2  
Trading Symbol MCRB  
Entity Registrant Name Seres Therapeutics, Inc.  
Entity Central Index Key 0001609809  
Current Fiscal Year End Date --12-31  
Entity Filer Category Non-accelerated Filer  
Entity Common Stock, Shares Outstanding   38,963,640