v3.23.3
Document and Entity Information - shares
 9 Months Ended
Sep. 30, 2023
Oct. 27, 2023
Cover [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Transition Report false  
Document Period End Date Sep. 30, 2023  
Entity File Number 001-35005  
Entity Registrant Name ASSEMBLY BIOSCIENCES, INC.  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 20-8729264  
Entity Address, Address Line One 331 Oyster Point Blvd.  
Entity Address, Address Line Two Fourth Floor  
Entity Address, City or Town South San Francisco  
Entity Address, State or Province CA  
Entity Address, Postal Zip Code 94080  
City Area Code 833  
Local Phone Number 509-4583  
Amendment Flag false  
Document Fiscal Year Focus 2023  
Document Fiscal Period Focus Q3  
Entity Central Index Key 0001426800  
Current Fiscal Year End Date --12-31  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Non-accelerated Filer  
Trading Symbol ASMB  
Security Exchange Name NASDAQ  
Title of 12(b) Security Common Stock, par value $0.001  
Entity Common Stock, Shares Outstanding   65,709,112
Entity Shell Company false  
Entity Emerging Growth Company false  
Entity Small Business true