Summary of Stock Option Activity (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Options
Beginning Balance	4,228
Granted	336
Exercised	(1,029)
Cancelled and expired	(43)
Ending Balance	3,492	4,228
Exercisable at end of year	2,708
Options vested and expected to vest at end of year	3,401
Weighted-Average Exercise Price
Beginning Balance	$ 11.49
Granted	$ 23.56
Exercised	$ 9.10
Cancelled and expired	$ 18.54
Ending Balance	$ 13.27	$ 11.49
Exercisable at end of year	$ 11.40
Options vested and expected to vest at end of year	$ 13.17
Weighted-Average Remaining Contractual Term (years)
Outstanding	4 years 11 months 1 day	5 years 4 months 13 days
Exercisable at end of year	3 years 11 months 23 days
Options vested and expected to vest at end of year	4 years 10 months 6 days
Aggregate Intrinsic Value
Outstanding at end of year	$ 44,634
Exercisable at end of year	39,653
Options vested and expected to vest at end of year	$ 43,819