Net Loss per Share - Schedule of Basic and Diluted Earnings (Loss) Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Numerator:
Net loss	$ (175,522)	$ (99,011)	$ (83,973)
Denominator:
Weighted-average shares used to compute net loss per share, basic and diluted (in shares)	55,939,032	52,034,596	23,718,391
Net loss per share, basic and diluted (in dollars per share)	$ (3.14)	$ (1.90)	$ (3.54)