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	12 Months Ended
	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2011
Numerator:
Net income	$ 18,188	$ 9,821	$ 13,929
Less: amount allocable to preference shareholders	(9,517)	(7,204)	(9,749)
Less: amount allocable to unvested early exercised options	(61)	(51)	(172)
Net income allocable to ordinary shareholders-basic	8,610	2,566	4,008
Undistributed earnings reallocated to ordinary shareholders	432	277	514
Net income allocable to ordinary shareholders-diluted	$ 9,042	$ 2,843	$ 4,522
Denominator:
Weighted-average ordinary shares outstanding	13,599,273	8,118,834	7,779,624
Less: weighted-average unvested early exercised options subject to repurchase	(87,627)	(156,890)	(320,997)
Weighted-average ordinary shares-basic	13,511,646	7,961,944	7,458,627
Effect of potentially dilutive securities:
Employee stock options	1,443,809	1,507,876	1,648,446
Restricted stock units	16,930
Employee stock purchase plan	27,230
Warrants to purchase ordinary shares	6,737
Over-allotment shares	10,634
Weighted-average ordinary shares-diluted	15,016,986	9,469,820	9,107,073
Net income per ordinary share:
Basic	$ 0.64	$ 0.32	$ 0.54
Diluted	$ 0.60	$ 0.30	$ 0.50