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		9 Months Ended
	Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2017	Oct. 31, 2016
Numerator:
Net loss attributable to common stockholders	$ (11,302)	$ (6,694)	$ (35,082)	$ (30,999)
Denominator:
Weighted-average number of shares used in computing net loss per share attributable to common stockholders, basic and diluted	53,779	18,420	52,388	9,987
Net loss per share attributable to common stockholders, basic and diluted	$ (0.21)	$ (0.36)	$ (0.67)	$ (3.10)