Net Loss per Share Attributable to Common Stockholders - Computation of Basic and Diluted Net Loss per Share Attributable to Common Stockholders (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2017	Jul. 31, 2016
Numerator:
Net loss attributable to common stockholders	$ (13,742)	$ (12,438)	$ (23,780)	$ (24,305)
Denominator:
Weighted-average number of shares used in computing net loss per share attributable to common stockholders, basic and diluted	52,749	5,826	51,681	5,721
Net loss per share attributable to common stockholders, basic and diluted	$ (0.26)	$ (2.13)	$ (0.46)	$ (4.25)