Basic and Diluted Net Loss Per Share - Potential Shares of Common Stock Excluded from Diluted Weighted-Average Common Shares Outstanding (Details) - shares	3 Months Ended		9 Months Ended
	Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2017	Oct. 31, 2016
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential shares excluded from diluted net loss per share	4,153,177	4,201,273	4,153,177	4,201,273
Employee stock purchase plan
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential shares excluded from diluted net loss per share	274,339	339,543	274,339	339,543
Options to purchase common stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential shares excluded from diluted net loss per share	1,812,890	1,796,127	1,812,890	1,796,127
Restricted stock units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential shares excluded from diluted net loss per share	2,047,136	1,901,233	2,047,136	1,901,233
Common stock subject to repurchase
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential shares excluded from diluted net loss per share	18,812	66,439	18,812	66,439
Warrants to purchase common stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potential shares excluded from diluted net loss per share		97,931		97,931