Share-based compensation - Summary of Stock Option Activity and Related Information (Parenthetical) (Detail) - CAD ($) $ / shares in Units, $ in Millions	12 Months Ended
Oct. 31, 2024	Oct. 31, 2023
Disclosure of terms and conditions of share-based payment arrangement [abstract]
Cash received for options exercised	$ 157	$ 63
Weighted average share price at the date of exercise	$ 144.69	$ 130.94

The weighted average share price at the date of exercise for share options that are exercised in a share-based payment arrangement. [Refer: Share-based payment arrangements [member]; Weighted average [member]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 2
-IssueDate 2023-01-01
-Paragraph 45
-Subparagraph c
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=2&code=ifrs-tx-2023-en-r&anchor=para_45_c&doctype=Standard
-URIDate 2023-03-23

Name:	ifrs-full_WeightedAverageExercisePriceOfShareOptionsInSharebasedPaymentArrangementExercisedDuringPeriodAtDateOfExercise2019
Namespace Prefix:	ifrs-full_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	duration