Short-Term Investments - Schedule of Fair Values and Gross Unrealized Loss Position of Available-for-Sale Securities Aggregated by Investment Category (Detail) - USD ($) $ in Thousands	Oct. 31, 2019	Jan. 31, 2019
Certificates of deposits
Schedule of Available-for-sale Securities [Line Items]
Fair value		$ 999
Gross unrealized losses		(1)
Asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Fair value	$ 9,545	69,131
Gross unrealized losses	(6)	(300)
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Fair value	10,561	7,155
Gross unrealized losses	(2)	(2)
Corporate notes and bonds
Schedule of Available-for-sale Securities [Line Items]
Fair value	27,851	121,006
Gross unrealized losses	(26)	(457)
Foreign government bonds
Schedule of Available-for-sale Securities [Line Items]
Fair value		1,490
Gross unrealized losses		(11)
U.S. agency obligations
Schedule of Available-for-sale Securities [Line Items]
Fair value		14,928
Gross unrealized losses		(2)
U.S. treasury securities
Schedule of Available-for-sale Securities [Line Items]
Fair value	33,093	130,785
Gross unrealized losses	$ (16)	$ (62)

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109979856&loc=d3e26610-111562

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

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- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27337-111563

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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