Summary of Stock Option Activity (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	9 Months Ended	12 Months Ended
	Dec. 31, 2014	Mar. 31, 2014
Options
Outstanding at April 1, 2014	3,492
Granted	319
Exercised	(723)
Cancelled and expired	(11)
Outstanding at December 31, 2014	3,077	3,492
Exercisable at December 31, 2014	2,307
Options vested and expected to vest at end of year	3,009
Weighted-Average Exercise Price
Outstanding at April 1, 2014	$ 13.27
Granted	$ 22.57
Exercised	$ 11.91
Cancelled and expired	$ 18.34
Outstanding at December 31, 2014	$ 14.54	$ 13.27
Exercisable at December 31, 2014	$ 11.96
Options vested and expected to vest at December 31, 2014	$ 14.35
Weighted-Average Remaining Contractual Term (years)
Outstanding	5 years 2 months 27 days	4 years 11 months 1 day
Exercisable at December 31, 2014	4 years 1 month 17 days
Options vested and expected to vest at December 31, 2014	5 years 1 month 28 days
Aggregate Intrinsic Value
Outstanding at December 31, 2014	$ 72,379
Exercisable at December 31, 2014	60,232
Options vested and expected to vest at December 31, 2014	$ 71,331