Common Stock - Summary of Reserved Shares of Authorized but Unissued Common Stock (Details) - shares	Jan. 31, 2018	Jan. 31, 2017
Class Of Stock [Line Items]
Shares reserved for future issuance	13,978,102	16,490,604
Convertible Preferred Stock
Class Of Stock [Line Items]
Shares reserved for future issuance		10,610,966
Convertible Preferred Stock Warrants
Class Of Stock [Line Items]
Shares reserved for future issuance		40,250
Options and RSUs Outstanding and Shares Available For Grant
Class Of Stock [Line Items]
Shares reserved for future issuance	12,080,540	5,814,388
Common Stock Warrants
Class Of Stock [Line Items]
Shares reserved for future issuance	1,897,562	25,000