Net Loss per Share Attributable to Common Stockholders - Net Loss per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 31, 2019	Oct. 31, 2018	Oct. 31, 2019	Oct. 31, 2018
Earnings Per Share [Abstract]
Net loss	$ (29,982)	$ (28,180)	$ (196,336)	$ (152,607)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted (in shares)	255,047	235,205	250,618	229,505
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.12)	$ (0.12)	$ (0.78)	$ (0.66)