v3.19.3
Cover Page - shares
9 Months Ended
Sep. 30, 2019
Oct. 31, 2019
Cover [Abstract]    
Document Type 10-Q  
Entity Interactive Data Current Yes  
Amendment Flag false  
Document Period End Date Sep. 30, 2019  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q3  
Entity Registrant Name CHIASMA, INC  
Entity Central Index Key 0001339469  
Current Fiscal Year End Date --12-31  
Entity Current Reporting Status Yes  
Entity Shell Company false  
Entity Filer Category Non-accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company true  
Entity Ex Transition Period true  
Entity Common Stock, Shares Outstanding   42,016,403
Trading Symbol CHMA  
Security Exchange Name NASDAQ  
Title of 12(b) Security Common Stock  
Entity Address, State or Province MA