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		6 Months Ended
	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2016	Jul. 31, 2015
Earnings Per Share [Abstract]
Net loss	$ (59,550)	$ (63,837)	$ (123,338)	$ (112,957)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted (in shares)	192,730	33,688	191,026	33,154
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.31)	$ (1.89)	$ (0.65)	$ (3.41)