v3.26.1
Changes in Accumulated other comprehensive income ("AOCI") by component (Details) - CAD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Beginning balance $ 47,416 $ 49,243 $ 46,825 $ 48,890
Net other comprehensive income (loss) 667 (1,756) 1,220 (1,784)
Ending balance 47,607 47,147 47,607 47,147
Accumulated other comprehensive income (loss)        
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Beginning balance 1,775 2,653 1,238 2,680
Other comprehensive income (loss) before reclassifications 650 (1,704) 1,187 (1,732)
Amounts reclassified from AOCI (1) 2 (1) 3
Net other comprehensive income (loss) 649 (1,702) 1,186 (1,729)
Ending balance 2,424 951 2,424 951
Foreign currency net of hedging activites        
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Beginning balance 2,365 3,385 1,829 3,413
Other comprehensive income (loss) before reclassifications 649 (1,707) 1,185 (1,735)
Amounts reclassified from AOCI 0 0 0 0
Net other comprehensive income (loss) 649 (1,707) 1,185 (1,735)
Ending balance 3,014 1,678 3,014 1,678
Derivatives        
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Beginning balance 8 10 9 10
Other comprehensive income (loss) before reclassifications 0 0 0 0
Amounts reclassified from AOCI (1) 1 (2) 1
Net other comprehensive income (loss) (1) 1 (2) 1
Ending balance 7 11 7 11
Pension and post - retirement defined benefit plans        
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Beginning balance (601) (737) (602) (738)
Other comprehensive income (loss) before reclassifications 0 0 0 0
Amounts reclassified from AOCI 0 1 1 2
Net other comprehensive income (loss) 0 1 1 2
Ending balance (601) (736) (601) (736)
Equity accounted investments        
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Beginning balance 3 (5) 2 (5)
Other comprehensive income (loss) before reclassifications 1 3 2 3
Amounts reclassified from AOCI 0 0 0 0
Net other comprehensive income (loss) 1 3 2 3
Ending balance $ 4 $ (2) $ 4 $ (2)