401(k) Plan - Additional Information (Details) - USD ($)	12 Months Ended
Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Defined Benefit Pension Plans And Defined Benefit Postretirement Plans Disclosure [Abstract]
Percentage of contributions under the saving plan, vested	100.00%
Defined benefit plan, contributions by plan eligible participants	$ 0	$ 0	$ 0

Amount of contributions received by defined benefit plan from participant which increases plan assets.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)(4)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

Name:	us-gaap_DefinedBenefitPlanPlanAssetsContributionsByPlanParticipant
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration