Summary of Restricted Stock Unit Activity (Parenthetical) (Detail)	12 Months Ended
Jan. 31, 2021 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Incremental shares released due to achievement of performance conditions \| shares	170,308
Market value on the last business day of the fiscal year \| $ / shares	$ 128.92

The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(2)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration