v3.26.1
employee future benefits - Defined benefit pension plans - summary (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
Other comprehensive income          
Discount rate used to determine defined benefit obligations 5.03%   5.03%   4.90%
Total $ 1 $ (36) $ (16) $ (35)  
Effect of asset ceiling          
Other comprehensive income          
Changes in the effect of limiting net defined benefit plan assets to the asset ceiling     1,463   $ 1,351
Pension plans | Pension plan | Plan assets          
Employee benefits expense          
Employees' contributions 5 5 9 9  
Administrative fees (1) (1) (2) (2)  
Total 4 4 7 7  
Financing costs          
Notional income on plan assets and interest on defined benefit obligations accrued 114 108 229 215  
Interest effect on asset ceiling limit (16) (15) (33) (29)  
Total 98 93 196 186  
Other comprehensive income          
Plan assets - Difference between actual results and estimated plan assumptions 216 (15) 153 38  
Changes in the effect of limiting net defined benefit plan assets to the asset ceiling (32) (99) (79) (103)  
Total 184 (114) 74 (65)  
AMOUNTS INCLUDED IN OPERATING ACTIVITIES CASH FLOWS          
Employer contributions     9 10  
BENEFITS PAID BY PLANS     (234) (234)  
PLAN ACCOUNT BALANCES          
Change in period     52 (96)  
Balance at beginning of period     8,258 8,262 8,262
Balance at end of period 8,310 8,166 8,310 8,166 8,258
Pension plans | Pension plan | Plan assets | Pension plans that have plan assets in excess of defined benefit obligations accrued          
PLAN ACCOUNT BALANCES          
Balance at end of period 8,301 8,157 8,301 8,157  
Pension plans | Pension plan | Plan assets | Pension plans that have defined benefit obligations accrued in excess of plan assets          
PLAN ACCOUNT BALANCES          
Balance at end of period 9 9 9 9  
Pension plans | Pension plan | Plan assets | Pension plans that have defined benefit obligations accrued in excess of plan assets - Funded          
PLAN ACCOUNT BALANCES          
Balance at end of period 9 9 9 9  
Pension plans | Pension plan | Defined benefit obligation accrued          
Employee benefits expense          
Benefits earned for current service (18) (18) (34) (36)  
Benefits earned for past service (4)   (4)    
Total (22) (18) (38) (36)  
Financing costs          
Notional income on plan assets and interest on defined benefit obligations accrued (102) (96) (203) (192)  
Total (102) (96) (203) (192)  
Other comprehensive income          
Changes in plan financial assumptions (185) 150 (58) 100  
Total (185) 150 (58) 100  
AMOUNTS INCLUDED IN OPERATING ACTIVITIES CASH FLOWS          
BENEFITS PAID BY PLANS     234 234  
PLAN ACCOUNT BALANCES          
Change in period     (65) 106  
Balance at beginning of period     (8,476) (8,452) (8,452)
Balance at end of period (8,541) (8,346) (8,541) (8,346) (8,476)
Pension plans | Pension plan | Defined benefit obligation accrued | Pension plans that have plan assets in excess of defined benefit obligations accrued          
PLAN ACCOUNT BALANCES          
Balance at end of period (8,067) (7,896) (8,067) (7,896)  
Pension plans | Pension plan | Defined benefit obligation accrued | Pension plans that have defined benefit obligations accrued in excess of plan assets          
PLAN ACCOUNT BALANCES          
Balance at end of period (474) (450) (474) (450)  
Pension plans | Pension plan | Defined benefit obligation accrued | Pension plans that have defined benefit obligations accrued in excess of plan assets - Funded          
PLAN ACCOUNT BALANCES          
Balance at end of period (254) (226) (254) (226)  
Pension plans | Pension plan | Defined benefit obligation accrued | Pension plans that have defined benefit obligations accrued in excess of plan assets - Unfunded          
PLAN ACCOUNT BALANCES          
Balance at end of period (220) (224) (220) (224)  
Pension plans | Pension plan | Net          
Employee benefits expense          
Total (18) (14) (31) (29)  
Financing costs          
Total (4) (3) (7) (6)  
DEFINED BENEFIT (COST) INCLUDED IN NET INCOME (22) (17) (38) (35)  
Other comprehensive income          
Total (1) 36 16 35  
DEFINED BENEFIT (COST) INCLUDED IN COMPREHENSIVE INCOME (23) 19 (22)    
AMOUNTS INCLUDED IN OPERATING ACTIVITIES CASH FLOWS          
Employer contributions     9 10  
PLAN ACCOUNT BALANCES          
Change in period     (13) 10  
Balance at beginning of period     (218) (190) (190)
Balance at end of period (231) (180) (231) (180) $ (218)
Pension plans | Pension plan | Net | Pension plans that have plan assets in excess of defined benefit obligations accrued          
PLAN ACCOUNT BALANCES          
Balance at end of period 234 261 234 261  
Pension plans | Pension plan | Net | Pension plans that have defined benefit obligations accrued in excess of plan assets          
PLAN ACCOUNT BALANCES          
Balance at end of period (465) (441) (465) (441)  
Pension plans | Pension plan | Net | Pension plans that have defined benefit obligations accrued in excess of plan assets - Funded          
PLAN ACCOUNT BALANCES          
Balance at end of period (245) (217) (245) (217)  
Pension plans | Pension plan | Net | Pension plans that have defined benefit obligations accrued in excess of plan assets - Unfunded          
PLAN ACCOUNT BALANCES          
Balance at end of period $ (220) $ (224) $ (220) $ (224)