v3.10.0.1
Document And Entity Information - shares
6 Months Ended
Jun. 30, 2018
Aug. 03, 2018
Document And Entity Information [Abstract]    
Entity Registrant Name Xenon Pharmaceuticals Inc.  
Document Type 10-Q  
Trading Symbol XENE  
Current Fiscal Year End Date --12-31  
Amendment Flag false  
Entity Central Index Key 0001582313  
Entity Filer Category Smaller Reporting Company  
Document Period End Date Jun. 30, 2018  
Document Fiscal Year Focus 2018  
Document Fiscal Period Focus Q2  
Entity Common Stock, Shares Outstanding   19,261,889