Net Loss Per Share Attributable to Common Stockholders (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Apr. 30, 2017	Apr. 30, 2016	Jan. 31, 2017
Earnings Per Share [Abstract]
Net loss attributable to common stockholders	$ (16,106)	$ (9,343)	$ (43,150)
Weighted-average common shares outstanding (in shares)	40,466,620	30,978,083
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.40)	$ (0.30)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive common equivalent shares	25,634,936	65,070,286
Convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive common equivalent shares	0	43,594,753
Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive common equivalent shares	35,000	85,000
Warrants | Series B
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive common equivalent shares	0	67,568
Warrants | Series C
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive common equivalent shares	0	43,369
Options to purchase common stock | Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive common equivalent shares	25,329,936	21,239,596
RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive common equivalent shares	270,000	40,000