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Income Taxes - Additional Information (Detail) - CAD ($)
$ in Millions
 1 Months Ended 12 Months Ended
Jun. 30, 2024
Oct. 31, 2025
Oct. 31, 2024
Oct. 31, 2023
Disclosure Of Income Taxes [Line Items]        
Net deferred tax assets   $ 980 $ 772 $ 607
Deferred tax assets   1,027 821  
Deferred tax liabilities   47 49  
Unused tax losses for which deferred tax assets have not been recognized   598 735  
Foreign exchange loss   $ 76    
Tax rate   1.00%    
Deferred tax operating loss carryforwards   $ 13 12  
2020 Taxation Year [Member]        
Disclosure Of Income Taxes [Line Items]        
Additional income tax by denying the tax deductibility   1,918    
Organization For Economic Cooperation And Development Pillar Two Tax Regime [Member]        
Disclosure Of Income Taxes [Line Items]        
Global minimum tax percentage 15.00%      
Caribbean [member]        
Disclosure Of Income Taxes [Line Items]        
Unused tax losses for which deferred tax assets have not been recognized   538 732  
Deferred tax operating loss carryforwards   $ 5    
Caribbean [member] | Top of range [member]        
Disclosure Of Income Taxes [Line Items]        
Unused tax losses for which deferred tax assets have not been recognized, expiration period   10    
Caribbean [member] | Bottom of range [member]        
Disclosure Of Income Taxes [Line Items]        
Unused tax losses for which deferred tax assets have not been recognized, expiration period   7    
Canada [member]        
Disclosure Of Income Taxes [Line Items]        
Unused tax losses for which deferred tax assets have not been recognized   $ 482 482  
Deferred tax operating loss carryforwards   7    
US [member]        
Disclosure Of Income Taxes [Line Items]        
Unused tax losses for which deferred tax assets have not been recognized   60 $ 3  
Deferred tax operating loss carryforwards   $ 1