Summary of Stock Option Activity (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Options
Outstanding at beginning of year	3,492
Granted	322
Exercised	(911)
Cancelled and expired	(11)
Outstanding at end of year	2,892	3,492
Exercisable at end of year	2,150
Options vested and expected to vest at end of year	2,827
Weighted-Average Exercise Price
Outstanding at beginning of year	$ 13.27
Granted	$ 22.83
Exercised	$ 11.99
Cancelled and expired	$ 18.34
Outstanding at end of year	$ 14.72	$ 13.27
Exercisable at end of year	$ 11.95
Options vested and expected to vest at end of year	$ 14.52
Weighted-Average Remaining Contractual Term (years)
Outstanding	5 years 2 months 5 days	4 years 11 months 1 day
Exercisable at end of year	4 years 29 days
Options vested and expected to vest at end of year	5 years 1 month 10 days
Aggregate Intrinsic Value
Outstanding at end of year	$ 164,439
Exercisable at end of year	128,200
Options vested and expected to vest at end of year	$ 161,304