Net Income per Share Attributable to Common Stockholders - Potential Common Share Equivalents Excluded where the Inclusion would be Anti-dilutive (Detail) - shares	12 Months Ended
Jan. 31, 2019	Jan. 31, 2018	Jan. 31, 2017
Earnings Per Share [Abstract]
Options and awards to purchase shares not included in the computation of diluted net income per share because their inclusion would be anti-dilutive	3,054,322	833,691	2,040,238

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

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