Stock Option Plan - Summary of Stock Option (Parenthetical) (Detail) - CAD ($)	12 Months Ended
Jan. 31, 2019	Jan. 31, 2018
Disclosure of detailed information about share based payment arrangements [abstract]
Weighted-average stock price on exercised stock options	$ 61.04	$ 39.78

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 2018-01-01
-Paragraph 45
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=2&date=2018-03-01&anchor=para_45_c&doctype=Standard
-URIDate 2018-03-16

Name:	ifrs-full_WeightedAverageExercisePriceOfShareOptionsInSharebasedPaymentArrangementExercisedDuringPeriodAtDateOfExercise
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration