Summary of Stock Option Activity (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	6 Months Ended	12 Months Ended
	Sep. 30, 2014	Mar. 31, 2014
Options
Outstanding at April 1, 2014	3,492
Granted	313
Exercised	(222)
Cancelled and expired	(5)
Outstanding at September 30, 2014	3,578	3,492
Exercisable at September 30, 2014	2,787
Options vested and expected to vest at end of year	3,502
Weighted-Average Exercise Price
Outstanding at April 1, 2014	$ 13.27
Granted	$ 22.26
Exercised	$ 11.49
Cancelled and expired	$ 15.66
Outstanding at September 30, 2014	$ 14.16	$ 13.27
Exercisable at September 30, 2014	$ 11.94
Options vested and expected to vest at September 30, 2014	$ 14.00
Weighted-Average Remaining Contractual Term (years)
Outstanding	5 years 15 days	4 years 11 months 1 day
Exercisable at September 30, 2014	3 years 11 months 27 days
Options vested and expected to vest at September 30, 2014	4 years 11 months 19 days
Aggregate Intrinsic Value
Outstanding at September 30, 2014	$ 38,287
Exercisable at September 30, 2014	35,928
Options vested and expected to vest at September 30, 2014	$ 38,013