Net Income Per Ordinary Share - Computation of Basic and Diluted Net Income Per Ordinary Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015
Numerator:
Net income	$ 57,810	$ 76,508	$ 50,571
Less: amount allocable to unvested early exercised options	0	0	(11)
Net income allocable to ordinary shareholders - basic	57,810	76,508	50,560
Undistributed earnings reallocated to ordinary shareholders	0	0	1
Net income allocable to ordinary shareholders - diluted	$ 57,810	$ 76,508	$ 50,561
Denominator:
Weighted-average ordinary shares outstanding	32,671,221	31,633,992	29,749,354
Less: weighted-average unvested early exercised options subject to repurchase	0	(56)	(6,701)
Weighted-average ordinary shares - basic	32,671,221	31,633,936	29,742,653
Effect of potentially dilutive securities:
Employee stock options	1,080,864	1,245,341	1,818,401
Restricted stock and restricted stock units	565,068	865,863	704,788
Employee stock purchase plan	10,571	10,569	12,285
Weighted-average ordinary shares - diluted	34,327,724	33,755,709	32,278,127
Net income per ordinary share:
Basic	$ 1.77	$ 2.42	$ 1.70
Diluted	$ 1.68	$ 2.27	$ 1.57