Net Loss Per Ordinary Share - Computation of Basic and Diluted Loss Per Ordinary Share (Detail) - 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	$ (17,078)	$ (14,756)	$ (15,463)	$ (4,309)	$ (10,191)	$ (17,311)	$ (47,297)	$ (31,811)
Denominator:
Weighted-average ordinary shares - basic	34,819,880			33,304,171			34,460,172	32,885,729
Weighted-average ordinary shares - diluted	34,819,880			33,304,171			34,460,172	32,885,729
Net loss per ordinary share:
Basic	$ (0.49)			$ (0.13)			$ (1.37)	$ (0.97)
Diluted	$ (0.49)			$ (0.13)			$ (1.37)	$ (0.97)