XML 53 R1.htm IDEA: XBRL DOCUMENT v3.19.3
Document and Entity Information - shares
 9 Months Ended
Sep. 30, 2019
Oct. 31, 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 ZFGN  
Entity Registrant Name ZAFGEN, INC.  
Entity Central Index Key 0001374690  
Current Fiscal Year End Date --12-31  
Entity Filer Category Accelerated Filer  
Entity Small Business true  
Entity Emerging Growth Company true  
Entity Ex Transition Period true  
Entity Common Stock, Shares Outstanding   37,374,118
Entity Current Reporting Status Yes  
Entity Shell Company false  
Entity File Number 001-36510  
Entity Tax Identification Number 20-3857670  
Entity Address, Address Line One 3 Center Plaza  
Entity Address, Address Line Two Suite 610  
Entity Address, City or Town Boston  
Entity Address, State or Province MA  
Entity Address, Postal Zip Code 02108  
City Area Code 617  
Local Phone Number 622-4003  
Title of 12(b) Security Common Stock  
Security Exchange Name NASDAQ  
Entity Interactive Data Current Yes  
Document Quarterly Report true  
Document Transition Report false