Stockholders' Equity - Summary of Reserved Shares of Common Stock for Future Issuance (Details) - shares	Jan. 31, 2017	Jan. 31, 2016
Class Of Stock [Line Items]
Shares underlying outstanding equity awards (in shares)	56,840,189	68,879,087
Shares reserved for future equity awards (in shares)	93,048,923
Employee stock purchase plan
Class Of Stock [Line Items]
Shares reserved for future equity awards (in shares)	2,968,087
Restricted stock units
Class Of Stock [Line Items]
Shares reserved for future equity awards (in shares)	8,783,024
Equity awards
Class Of Stock [Line Items]
Shares reserved for future equity awards (in shares)	24,457,623

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Aggregate number of common shares reserved for future issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.29)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Number of options outstanding, including both vested and non-vested options.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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