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Income Taxes - Additional Information (Detail) - CAD ($)
$ in Millions
 12 Months Ended
Oct. 31, 2025
Oct. 31, 2024
Oct. 31, 2023
Disclosure of Income Tax [Line items]      
Deferred income tax assets loss carryforwards $ 2,732 $ 3,024 $ 3,420
Temporary differences, unused tax losses and unused tax credits for which no deferred tax asset is recognized 917 947  
Temporary differences associated with repatriation of earnings from investments in subsidiaries, branches and associates and interests in joint arrangements for which deferred tax liabilities have not been recognised 31,000 27,000  
Less than five years expiry [Member]      
Disclosure of Income Tax [Line items]      
Unused tax losses for which no deferred tax asset recognised 52 53  
2011 - 2018 taxation years [member]      
Disclosure of Income Tax [Line items]      
Additional income tax expense and interest 1,465    
Canada [member] | Tax loss carryforwards [member]      
Disclosure of Income Tax [Line items]      
Deferred income tax assets loss carryforwards 50 20  
United States [member] | Tax loss carryforwards [member]      
Disclosure of Income Tax [Line items]      
Deferred income tax assets loss carryforwards $ 4 $ 3