v3.25.4
Financial instruments (Cross-Currency Interest Rate Swaps) (Details) - CAD ($)
 12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Other income (expense) $ (88,000,000) $ (42,000,000) $ (134,000,000)
Foreign currency exposure 913,000,000 891,000,000 $ 722,000,000
Derivative asset 0 38,000,000  
Derivative liability 10,000,000 $ 0  
Cross Currency Interest Rate Contract      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Notional amount 975,000,000    
Principal amount $ 1,401,000,000    
Weighted average interest rate 3.33%    
Loss on derivative $ 45,000,000    
Derivative asset 7,000,000    
Derivative liability 29,000,000    
Other liabilities and deferred credits 30,000,000    
Cross Currency Interest Rate Contract | Reclassification out of Accumulated Other Comprehensive Income | Derivative instruments      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Other income (expense) 62,000,000    
Foreign currency exposure $ 14,000,000