v3.25.4
Employee Future Benefits - Additional Information (Details) - CAD ($)
$ in Millions
12 Months Ended
Dec. 31, 2026
Dec. 31, 2025
Dec. 31, 2024
Pension plans      
Disclosure of defined benefit plans [line items]      
Estimate of expected cash payments for employee future benefits for the year ending December 31, 2025 $ 57    
Defined contribution plans      
Disclosure of defined benefit plans [line items]      
Estimate of expected cash payments for employee future benefits for the year ending December 31, 2025 117    
Retiree welfare plans      
Disclosure of defined benefit plans [line items]      
Estimate of expected cash payments for employee future benefits for the year ending December 31, 2025 $ 18    
Canadian plans      
Disclosure of defined benefit plans [line items]      
Estimate of expected cash payments for employee future benefits for the year ending December 31, 2025   $ 2  
Return-Seeking Assets      
Disclosure of defined benefit plans [line items]      
Target asset allocation for plan   30.00% 30.00%
Return-Seeking Assets | Canada      
Disclosure of defined benefit plans [line items]      
Target asset allocation for plan   17.00% 17.00%
Liability-Hedging Assets      
Disclosure of defined benefit plans [line items]      
Target asset allocation for plan   70.00% 70.00%
Liability-Hedging Assets | Canada      
Disclosure of defined benefit plans [line items]      
Target asset allocation for plan   83.00% 83.00%