Net Loss per Share Attributable to Common Stockholders - Potentially Dilutive Securities Not Included in Diluted per Share Calculations (Details) - shares	12 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share	13,574,086	44,537,940	37,791,639
Convertible preferred stock as converted
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share		34,610,979	29,666,693
Employee Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share	13,016,402	9,543,966	7,591,950
RSUs
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share	77,883	62,500
Unvested common shares subject to repurchase
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share	335,116	283,524	335,502
Shares committed under 2016 ESPP
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share	144,685
Convertible preferred stock warrants
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of earnings per share		36,971	197,494