v3.25.4
Cover - shares
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Document Information [Line Items]    
Document Type 40-F  
Document Registration Statement false  
Document Annual Report true  
Current Fiscal Year End Date --12-31  
Document Period End Date Dec. 31, 2025  
Entity File Number 001-39974  
Entity Registrant Name WEST FRASER TIMBER CO. LTD.  
Entity Incorporation, State or Country Code A1  
Entity Tax Identification Number 98-1630330  
Entity Address, Address Line One 1500 – 885 West Georgia Street  
Entity Address, City or Town Vancouver  
Entity Address, State or Province BC  
Entity Address, Country CA  
Entity Address, Postal Zip Code V6C 3E8  
City Area Code 604  
Local Phone Number 895-2700  
Title of 12(b) Security Common Shares, no par value  
Trading Symbol WFG  
Security Exchange Name NYSE  
Annual Information Form true  
Audited Annual Financial Statements true  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Emerging Growth Company false  
ICFR Auditor Attestation Flag true  
Document Financial Statement Error Correction [Flag] false  
Entity Central Index Key 0001402388  
Document Fiscal Year Focus 2025  
Document Fiscal Period Focus FY  
Amendment Flag false  
Classes of share capital    
Document Information [Line Items]    
Number of shares issued 78,299,822 79,988,266
Business Contact    
Document Information [Line Items]    
Contact Personnel Name West Fraser, Inc.  
Entity Address, Address Line One 57 Germantown Court  
Entity Address, Address Line Two Suite 300  
Entity Address, City or Town Cordova  
Entity Address, State or Province TN  
Entity Address, Postal Zip Code 38018-4274  
City Area Code 901  
Local Phone Number 620-4200