Stock-based Compensation - Stock Option Activities (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended
	Oct. 31, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares, Outstanding	4,344,535
Shares, Granted	192,220
Shares, Exercised	(713,498)
Shares, Forfeited	(59,901)
Shares, Outstanding	3,763,356
Shares, Exercisable	2,839,311
Shares, Vested and expected to vest	3,715,813
Weighted-Average Exercise Price, Outstanding	$ 6.07
Weighted-Average Exercise Price, Granted	$ 15.90
Weighted-Average Exercise Price, Exercised	$ 5.33
Weighted-Average Exercise Price, Forfeited	$ 9.88
Weighted-Average Exercise Price, Outstanding	$ 6.65
Weighted-Average Exercise Price, Exercisable	$ 5.62
Weighted-Average Exercise Price, Vested and expected to vest	$ 6.60
Weighted-Average Grant-date Fair Value, Granted	$ 9.50
Total Intrinsic Value of options Exercised, Exercised	$ 8,239
Weighted-Average Remaining Contractual Term, Outstanding	6 years 5 months 9 days
Weighted-Average Remaining Contractual Term, Exercisable	5 years 10 months 17 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest	6 years 4 months 28 days
Aggregate Intrinsic Value, Outstanding	52,314
Aggregate Intrinsic Value, Exercisable	42,405
Aggregate Intrinsic Value, Vested and expected to vest	$ 51,819