v3.8.0.1
Document And Entity Information
12 Months Ended
Dec. 31, 2017
shares
Document Information [Line Items]  
Entity Registrant Name Clementia Pharmaceuticals Inc.
Entity Central Index Key 0001647320
Trading Symbol cmta
Current Fiscal Year End Date --12-31
Entity Filer Category Non-accelerated Filer
Entity Current Reporting Status Yes
Entity Voluntary Filers No
Entity Well-known Seasoned Issuer No
Entity Common Stock, Shares Outstanding (in shares) 31,717,584
Document Type 20-F
Document Period End Date Dec. 31, 2017
Document Fiscal Year Focus 2017
Document Fiscal Period Focus FY
Amendment Flag false