Net Income Per Ordinary Share - Computation of Basic and Diluted Net Income Per Ordinary Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2017	Jul. 31, 2016
Numerator:
Net income	$ 3,303	$ 8,632	$ 5,867	$ 10,415
Denominator:
Weighted-average ordinary shares - basic	33,227,717	32,557,398	33,240,767	32,492,723
Effect of potentially dilutive securities:
Employee stock options	984,064	1,074,331	995,107	1,062,310
Restricted stock and restricted stock units	356,253	530,279	389,498	498,128
Employee stock purchase plan	4,893	13,458	3,632	9,942
Weighted-average ordinary shares - diluted	34,572,927	34,175,466	34,629,004	34,063,103
Net income per ordinary share:
Basic	$ 0.10	$ 0.27	$ 0.18	$ 0.32
Diluted	$ 0.10	$ 0.25	$ 0.17	$ 0.31