Stock Options Outstanding (Detail) (USD $)	6 Months Ended
	Sep. 30, 2014
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Options Outstanding, Number of Shares Outstanding	1,592,230
Options Outstanding, Weighted-Average Remaining Contractual Life	6 years 10 months 10 days
Options Outstanding, Weighted-Average Exercise Price	$ 44.50
Options Exercisable, Number of Shares Outstanding	1,037,331
Options Exercisable, Weighted-Average Exercise Price	$ 34.33
$23.17 - $30.74 [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Range	$ 23.17
Range of Exercise Prices, Upper Range	$ 30.74
Options Outstanding, Number of Shares Outstanding	594,310
Options Outstanding, Weighted-Average Remaining Contractual Life	4 years 8 months 9 days
Options Outstanding, Weighted-Average Exercise Price	$ 26.50
Options Exercisable, Number of Shares Outstanding	591,310
Options Exercisable, Weighted-Average Exercise Price	$ 26.48
$33.08 - $40.78 [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Range	$ 33.08
Range of Exercise Prices, Upper Range	$ 40.78
Options Outstanding, Number of Shares Outstanding	492,533
Options Outstanding, Weighted-Average Remaining Contractual Life	7 years 4 months 6 days
Options Outstanding, Weighted-Average Exercise Price	$ 33.97
Options Exercisable, Number of Shares Outstanding	312,917
Options Exercisable, Weighted-Average Exercise Price	$ 34.02
$53.22 – $ 74.10 [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Range	$ 53.22
Range of Exercise Prices, Upper Range	$ 74.10
Options Outstanding, Number of Shares Outstanding	283,236
Options Outstanding, Weighted-Average Remaining Contractual Life	8 years 3 months 26 days
Options Outstanding, Weighted-Average Exercise Price	$ 66.58
Options Exercisable, Number of Shares Outstanding	114,589
Options Exercisable, Weighted-Average Exercise Price	$ 66.37
$87.34 – $ 93.56 [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Range	$ 87.34
Range of Exercise Prices, Upper Range	$ 93.56
Options Outstanding, Number of Shares Outstanding	222,151
Options Outstanding, Weighted-Average Remaining Contractual Life	9 years 8 months 5 days
Options Outstanding, Weighted-Average Exercise Price	$ 87.89
Options Exercisable, Number of Shares Outstanding	18,515
Options Exercisable, Weighted-Average Exercise Price	$ 91.95