Net Loss Per Ordinary Share - Computation of Basic and Diluted Loss Per Ordinary Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended
	Jul. 31, 2019	Apr. 30, 2019	Jul. 31, 2018	Apr. 30, 2018	Jul. 31, 2019	Jul. 31, 2018
Numerator:
Net loss	$ (10,191)	$ (17,311)	$ (6,877)	$ (10,006)	$ (27,502)	$ (16,883)
Denominator:
Weighted-average ordinary shares - basic	32,860,974		33,219,152		32,676,509	33,276,976
Weighted-average ordinary shares - diluted	32,860,974		33,219,152		32,676,509	33,276,976
Net loss per ordinary share:
Basic	$ (0.31)		$ (0.21)		$ (0.84)	$ (0.51)
Diluted	$ (0.31)		$ (0.21)		$ (0.84)	$ (0.51)