Net Loss Per Ordinary Share - Computation of Basic and Diluted Loss Per Ordinary Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Apr. 30, 2019	Apr. 30, 2018
Numerator:
Net loss	$ (17,311)	$ (10,006)
Denominator:
Weighted-average ordinary shares - basic	32,492,044	33,334,801
Weighted-average ordinary shares - diluted	32,492,044	33,334,801
Net loss per ordinary share:
Basic	$ (0.53)	$ (0.30)
Diluted	$ (0.53)	$ (0.30)