Stockholders' Equity - Summary of Reserved Shares of Common Stock for Future Issuance (Details) - shares	Jan. 31, 2018	Jan. 31, 2017
Class of Stock [Line Items]
Shares underlying outstanding equity awards (in shares)	46,359,949	56,840,189
Shares reserved for future equity awards (in shares)	86,217,278.00
Employee stock purchase plan
Class of Stock [Line Items]
Shares reserved for future equity awards (in shares)	2,489,767
Restricted stock units
Class of Stock [Line Items]
Shares reserved for future equity awards (in shares)	17,682,646
Employee Stock Options
Class of Stock [Line Items]
Shares reserved for future equity awards (in shares)	19,684,916