Capital Stock - Schedule of Ordinary Shares Reserved for Future Issuance under EIP and ESPP (Detail) - shares	Oct. 31, 2018	Jan. 31, 2018
EIP [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved	6,173,834	5,561,653
ESPP [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares reserved	1,833,574	1,561,841

Aggregate number of common shares reserved for future issuance.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.29)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_CommonStockCapitalSharesReservedForFutureIssuance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant