Post-Employment Benefits - Summary of Defined Contributions Plan Expense (Detail) - CAD ($) $ in Millions	3 Months Ended	9 Months Ended
Jul. 31, 2025	Apr. 30, 2025	Jul. 31, 2024	Jul. 31, 2025	Jul. 31, 2024
Disclosure of defined contribution plans [line items]
Expense recognized in consolidated statement of income	$ 77	$ 81	$ 69	$ 234	$ 202
Defined contribution pension plans [member]
Disclosure of defined contribution plans [line items]
Expense recognized in consolidated statement of income	20	23	17	63	55
Government pension plans [member]
Disclosure of defined contribution plans [line items]
Expense recognized in consolidated statement of income	$ 57	$ 58	$ 52	$ 171	$ 147

The amount of post-employment benefit expense relating to defined contribution plans. Defined contribution plans are post-employment benefit plans under which an entity pays fixed contributions into a separate entity (a fund) and will have no legal or constructive obligation to pay further contributions if the fund does not hold sufficient assets to pay all employee benefits relating to employee service in the current and prior periods.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 19
-IssueDate 2024-01-01
-Paragraph 53
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=19&code=ifrs-tx-2024-en-r&anchor=para_53&doctype=Standard
-URIDate 2024-03-27

Name:	ifrs-full_PostemploymentBenefitExpenseDefinedContributionPlans
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration