v3.25.4
Income taxes (Narrative) (Details) - CAD ($)
$ in Millions
 3 Months Ended 12 Months Ended
Dec. 31, 2023
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Income Tax Examination [Line Items]          
Deferred income taxes   $ (334) $ (325) $ 288  
Future taxable income to realize deferred income tax assets   3,300      
Gross unrecognized tax benefits $ 46 41 41 46 $ 52
Net unrecognized tax benefits at end of year $ 32 25 28 32  
Deferred tax expense (recovery)   (3) 4 1  
Accrued interest and penalties   15 $ 18    
Non-US          
Income Tax Examination [Line Items]          
Amortization period 10 years        
Deferred income taxes       682  
Deferred income tax recovery $ 767     767  
Income tax expense related to the foregone tax deduction       85  
Unamortized tax deductible goodwill   $ 5,200      
Non-US | Tax Year 2023          
Income Tax Examination [Line Items]          
Income tax expense related to the foregone tax deduction       31  
Non-US | Tax Years Prior To 2023          
Income Tax Examination [Line Items]          
Income tax expense related to the foregone tax deduction       $ 54