Summary of Stock Option Activity (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	9 Months Ended
	Dec. 31, 2012
Options
Beginning Balance	4,268
Granted	323
Exercised	(313)
Cancelled and expired	(63)
Ending Balance	4,215
Exercisable at December 31, 2012	3,214
Options vested and expected to vest at December 31, 2012	3,985
Weighted Average Exercise Price
Beginning Balance	$ 10.42
Granted	$ 22.32
Exercised	$ 8.73
Cancelled and expired	$ 10.22
Ending Balance	$ 11.44
Exercisable at December 31, 2012	$ 10.81
Options vested and expected to vest at December 31, 2012	$ 11.43
Weighted Average Remaining Contractual Term (years)
Beginning Balance	6 years 11 days
Ending Balance	5 years 6 months 18 days
Exercisable at December 31, 2012	4 years 9 months 26 days
Options vested and expected to vest at December 31, 2012	5 years 5 months 5 days
Aggregate Intrinsic Value
Outstanding at December 31, 2012	$ 12,688
Exercisable at December 31, 2012	9,571
Options vested and expected to vest at December 31, 2012	$ 11,825