Net Income (Loss) Per Ordinary Share - Computation of Basic and Diluted Net Income (Loss) Per Ordinary Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Jan. 31, 2019	Jan. 31, 2018	Jan. 31, 2017
Numerator:
Net income (loss)	$ (30,447)	$ 18,852	$ 57,810
Denominator:
Weighted-average ordinary shares - basic	32,713,606	33,224,803	32,671,221
Effect of dilutive securities:
Employee stock options	0	961,797	1,080,864
Restricted stock and restricted stock units	0	390,145	565,068
Employee stock purchase plan	0	6,405	10,571
Weighted-average ordinary shares - diluted	32,713,606	34,583,150	34,327,724
Net income (loss) per ordinary share:
Basic	$ (0.93)	$ 0.57	$ 1.77
Diluted	$ (0.93)	$ 0.55	$ 1.68