Net Income Per Ordinary Share - Computation of Basic and Diluted Net Income Per Ordinary Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Apr. 30, 2015	Apr. 30, 2014
Numerator:
Net income	$ 18,854	$ 5,260
Less: amount allocable to unvested early exercised options	0	(2)
Net income allocable to ordinary shareholders - basic	18,854	5,258
Undistributed earnings reallocated to ordinary shareholders	0	0
Net income allocable to ordinary shareholders - diluted	$ 18,854	$ 5,258
Denominator:
Weighted-average ordinary shares outstanding	31,099,137	28,986,938
Less: weighted-average unvested early exercised options subject to repurchase	(56)	(10,599)
Weighted-average ordinary shares - basic	31,099,081	28,976,339
Effect of potentially dilutive securities:
Employee stock options	1,397,695	2,110,757
Restricted stock units	961,284	655,502
Employee stock purchase plan	14,249	21,395
Weighted-average ordinary shares - diluted	33,472,309	31,763,993
Net income per ordinary share:
Basic	$ 0.61	$ 0.18
Diluted	$ 0.56	$ 0.17