Balance Sheet Components - Summary of Internal Use Software Costs (Parenthetical) (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
Jul. 31, 2019	Jan. 31, 2019
Property Plant And Equipment [Abstract]
Capitalized stock-based compensation expenses	$ 3.2	$ 0.8

Amount of cost capitalized for award under share-based payment arrangement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(ii)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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