Net Loss per Share Attributable to Common Stockholders - Summary of 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
	Apr. 30, 2017	Apr. 30, 2016
Earnings Per Share [Abstract]
Net loss	$ (62,374)	$ (63,788)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted (in shares)	205,783	189,283
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.30)	$ (0.34)