Organization and Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	Jul. 31, 2018	Jan. 31, 2018
Summary Of Significant Accounting Policies [Line Items]
Accumulated amortization of intangible asset	$ 5,389,000	$ 3,087,000
IPR&D [Member]
Summary Of Significant Accounting Policies [Line Items]
Accumulated amortization of intangible asset	$ 0	$ 0

Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

Name:	us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant