Net Loss Per Share - Schedule of Basic and Diluted Earnings (Loss) Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Oct. 31, 2020	Jul. 31, 2020	Apr. 30, 2020	Oct. 31, 2019	Jul. 31, 2019	Apr. 30, 2019	Oct. 31, 2020	Oct. 31, 2019
Numerator:
Net loss	$ (72,651)	$ (64,525)	$ (53,967)	$ (42,383)	$ (37,336)	$ (33,240)	$ (191,143)	$ (112,959)
Denominator:
Weighted-average shares used to compute net loss per share, basic and diluted (in shares)	59,368,167			56,411,779			58,476,521	55,600,484
Net loss per share, basic and diluted (in dollars per share)	$ (1.22)			$ (0.75)			$ (3.27)	$ (2.03)