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		9 Months Ended
	Oct. 31, 2016	Oct. 31, 2015	Oct. 31, 2016	Oct. 31, 2015
Earnings Per Share [Abstract]
Net loss	$ (78,813)	$ (56,501)	$ (202,151)	$ (169,458)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted (in shares)	195,807	74,565	192,637	47,109
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.40)	$ (0.76)	$ (1.05)	$ (3.60)