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		9 Months Ended
	Oct. 31, 2016	Oct. 31, 2015	Oct. 31, 2016	Oct. 31, 2015
Numerator:
Net income	$ 29,045	$ 29,461	$ 39,460	$ 71,412
Less: amount allocable to unvested early exercised options	0	0	0	0
Net income allocable to ordinary shareholders - basic	29,045	29,461	39,460	71,412
Undistributed earnings reallocated to ordinary shareholders	0	0	0	0
Net income allocable to ordinary shareholders - diluted	$ 29,045	$ 29,461	$ 39,460	$ 71,412
Denominator:
Weighted-average ordinary shares outstanding	32,670,784	31,815,588	32,552,077	31,476,724
Less: weighted-average unvested early exercised options subject to repurchase	0	0	0	(56)
Weighted-average ordinary shares - basic	32,670,784	31,815,588	32,552,077	31,476,668
Effect of potentially dilutive securities:
Employee stock options	1,159,739	1,199,065	1,094,786	1,316,228
Restricted stock and restricted stock units	753,178	881,605	583,144	957,263
Employee stock purchase plan	16,291	2,944	12,058	8,382
Weighted-average ordinary shares - diluted	34,599,992	33,899,202	34,242,065	33,758,541
Net income per ordinary share:
Basic	$ 0.89	$ 0.93	$ 1.21	$ 2.27
Diluted	$ 0.84	$ 0.87	$ 1.15	$ 2.12