v3.25.2
Employee retirement benefits - Components of Net Periodic Benefit Cost (Detail) - CAD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Jun. 30, 2024
Jun. 30, 2025
Jun. 30, 2024
Pension benefits:        
Service cost $ 46 $ 46 $ 93 $ 92
Interest cost 91 92 184 183
Expected return on plan assets (98) (114) (197) (227)
Amortization of prior service cost (credit) 8 7 14 14
Amortization of actuarial loss (gain) 3 12 6 24
Net benefit cost 50 43 100 86
Other postretirement benefits:        
Service cost 1 3 2 7
Interest cost 6 6 11 12
Amortization of prior service cost (credit) (1) 0 (2) 0
Amortization of actuarial loss (gain) (3) (2) (5) (4)
Net benefit cost $ 3 $ 7 $ 6 $ 15