Convertible Senior Notes - Carrying Amount Of Equity Component (Details) - Convertible Debt - Convertible Senior Notes Due 2023 - USD ($) $ in Thousands	Jan. 31, 2020	Jan. 31, 2019
Debt Instrument [Line Items]
Proceeds allocated to the conversion option (debt discount)	$ 134,667	$ 134,667
Less: transaction costs	(3,336)	(3,336)
Net carrying amount	$ 131,331	$ 131,331

The carrying amount of the equity component of convertible debt which may be settled in cash upon conversion.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870

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