v3.8.0.1
Document And Entity Information - shares
9 Months Ended
Sep. 30, 2017
Nov. 03, 2017
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 Accelerated Filer  
Document Period End Date Sep. 30, 2017  
Document Fiscal Year Focus 2017  
Document Fiscal Period Focus Q3  
Entity Common Stock, Shares Outstanding   17,998,420