v3.26.1
financial instruments - Market risks (Details) - CAD ($)
$ in Millions
 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Interest rate risk    
Market risks    
Percentage of reasonably possible changes in market risk variable 0.25% 0.25%
Net income sensitivity to increase in risk variable $ (6) $ (3)
Other comprehensive income sensitivity to increase in risk variable 4 (14)
Comprehensive income sensitivity to increase in risk variable (2) (17)
Net income sensitivity to decrease in risk variable 5 3
Other comprehensive income sensitivity to decrease in risk variable (4) 14
Comprehensive income sensitivity to decrease in risk variable $ 1 $ 17
Wind discount risk    
Market risks    
Percentage of reasonably possible changes in market risk variable 0.20% 0.20%
Other comprehensive income sensitivity to increase in risk variable $ (24) $ (22)
Comprehensive income sensitivity to increase in risk variable (24) (22)
Other comprehensive income sensitivity to decrease in risk variable 25 22
Comprehensive income sensitivity to decrease in risk variable $ 25 $ 22
Solar premium risk    
Market risks    
Percentage of reasonably possible changes in market risk variable 0.20% 0.20%
Other comprehensive income sensitivity to increase in risk variable $ 13 $ 12
Comprehensive income sensitivity to increase in risk variable 13 12
Other comprehensive income sensitivity to decrease in risk variable (14) (12)
Comprehensive income sensitivity to decrease in risk variable $ (14) $ (12)
Canadian Dollars | Currency risk    
Market risks    
Percentage of reasonably possible changes in market risk variable 10.00% 10.00%
Net income sensitivity to increase in risk variable   $ (6)
Other comprehensive income sensitivity to increase in risk variable $ (57) 47
Comprehensive income sensitivity to increase in risk variable (57) 41
Net income sensitivity to decrease in risk variable   6
Other comprehensive income sensitivity to decrease in risk variable 57 (39)
Comprehensive income sensitivity to decrease in risk variable 57 (33)
Canadian Dollars | Interest rate risk    
Market risks    
Net income sensitivity to increase in risk variable (4) (3)
Other comprehensive income sensitivity to increase in risk variable 102 72
Comprehensive income sensitivity to increase in risk variable 98 69
Net income sensitivity to decrease in risk variable 4 3
Other comprehensive income sensitivity to decrease in risk variable (106) (75)
Comprehensive income sensitivity to decrease in risk variable $ (102) $ (72)
U.S. Dollars | Currency risk    
Market risks    
Percentage of reasonably possible changes in market risk variable 10.00% 10.00%
Net income sensitivity to increase in risk variable $ (40) $ 14
Other comprehensive income sensitivity to increase in risk variable (13) (73)
Comprehensive income sensitivity to increase in risk variable (53) (59)
Net income sensitivity to decrease in risk variable 40 (14)
Other comprehensive income sensitivity to decrease in risk variable 13 73
Comprehensive income sensitivity to decrease in risk variable 53 59
U.S. Dollars | Interest rate risk    
Market risks    
Net income sensitivity to increase in risk variable (2)  
Other comprehensive income sensitivity to increase in risk variable (98) (86)
Comprehensive income sensitivity to increase in risk variable (100) (86)
Net income sensitivity to decrease in risk variable 1  
Other comprehensive income sensitivity to decrease in risk variable 102 89
Comprehensive income sensitivity to decrease in risk variable $ 103 $ 89