v3.26.1
financial instruments - Derivative gains and losses (Details) - CAD ($)
$ in Millions
3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Dec. 31, 2025
Derivative assets          
financial instruments          
Amount of gain (loss) recognized in other comprehensive income (effective portion) $ 75 $ (308) $ 250 $ (306)  
Gain (loss) reclassified from other comprehensive income to income (effective portion) 222 (325) 397 (317)  
Derivative assets | Currency risk          
financial instruments          
Amount of gain (loss) recognized in other comprehensive income (effective portion) 67 (343) 268 (323)  
Gain (loss) reclassified from other comprehensive income to income (effective portion) 220 (326) 394 (320)  
Derivative assets | Other market risk          
financial instruments          
Amount of gain (loss) recognized in other comprehensive income (effective portion) 8 35 (18) 17  
Gain (loss) reclassified from other comprehensive income to income (effective portion) 2 1 3 3  
Derivatives held for hedging | Currency risk related to purchases | U.S. Dollars | Goods and services purchased          
financial instruments          
Amount of gain (loss) recognized in other comprehensive income (effective portion) 10 (24) 21 (23)  
Gain (loss) reclassified from other comprehensive income to income (effective portion) 3 1   7  
Derivatives held for hedging | Currency risk related to long-term debt | U.S. Dollars | Financing costs          
financial instruments          
Amount of gain (loss) recognized in other comprehensive income (effective portion) 57 (268) 247 (228)  
Gain (loss) reclassified from other comprehensive income to income (effective portion) 217 (328) 394 (333)  
Spread included in fair value of derivative instruments 10 8 15 (8)  
Derivatives held for hedging | Currency risk related to investment in a foreign operation | Financing costs          
financial instruments          
Amount of gain (loss) recognized in other comprehensive income (effective portion)   (51)   (72)  
Gain (loss) reclassified from other comprehensive income to income (effective portion)   1   6  
Derivatives held for hedging | Other market risk | Financing costs          
financial instruments          
Amount of gain (loss) recognized in other comprehensive income (effective portion)       (2)  
Gain (loss) reclassified from other comprehensive income to income (effective portion)   1   1  
Derivatives held for trading | Currency risk | Financing costs          
financial instruments          
Gain (loss) on derivatives recognized in income (7) (1) (8) (6)  
Cash flow hedges | Derivative assets | Currency risk related to long-term debt | U.S. Dollars          
financial instruments          
Spread included in fair value of derivative instruments     (24)   $ (22)
Cash flow hedges | Derivatives held for hedging          
financial instruments          
Ineffective portion of derivative instruments classified as cash flow hedging items 0 0 0 0  
Cash flow hedges | Derivatives held for hedging | Other market risk | Goods and services purchased          
financial instruments          
Amount of gain (loss) recognized in other comprehensive income (effective portion) 8 35 (18) 19  
Gain (loss) reclassified from other comprehensive income to income (effective portion) 2   $ 3 2  
Ineffective portion of derivative instruments classified as cash flow hedging items $ (1) $ 2   $ 3