v3.8.0.1
Document And Entity Information - USD ($)
$ in Millions
12 Months Ended
Mar. 31, 2018
Jun. 28, 2018
Sep. 29, 2017
Document Information [Line Items]      
Document Type 10-K    
Amendment Flag false    
Document Period End Date Mar. 31, 2018    
Document Fiscal Year Focus 2018    
Document Fiscal Period Focus FY    
Entity Registrant Name Constellation Alpha Capital Corp.    
Entity Central Index Key 0001651944    
Current Fiscal Year End Date --03-31    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Filer Category Non-accelerated Filer    
Entity Public Float     $ 142.8
Trading Symbol CNACU    
Entity Common Stock, Shares Outstanding   18,530,000