Net Income (Loss) Per Ordinary Share - Computation of Basic and Diluted Net Income (Loss) Per Ordinary Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2018	Jul. 31, 2017	Jul. 31, 2018	Jul. 31, 2017
Numerator:
Net income (loss)	$ (6,877)	$ 3,303	$ (16,883)	$ 5,867
Denominator:
Weighted-average ordinary shares - basic	33,219,152	33,227,717	33,276,976	33,240,767
Effect of potentially dilutive securities:
Employee stock options	0	984,064	0	995,107
Restricted stock and restricted stock units	0	356,253	0	389,498
Employee stock purchase plan	0	4,893	0	3,632
Weighted-average ordinary shares - diluted	33,219,152	34,572,927	33,276,976	34,629,004
Net income (loss) per ordinary share:
Basic	$ (0.21)	$ 0.10	$ (0.51)	$ 0.18
Diluted	$ (0.21)	$ 0.10	$ (0.51)	$ 0.17