v3.8.0.1
Document and Entity Information - shares
3 Months Ended
Mar. 31, 2018
May 07, 2018
Document And Entity Information [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Mar. 31, 2018  
Document Fiscal Year Focus 2018  
Document Fiscal Period Focus Q1  
Trading Symbol CHMA  
Entity Registrant Name CHIASMA, INC  
Entity Central Index Key 0001339469  
Current Fiscal Year End Date --12-31  
Entity Filer Category Non-accelerated Filer  
Entity Common Stock, Shares Outstanding   24,383,994