Stock Options Outstanding (Detail) (USD $)	12 Months Ended
	Mar. 31, 2015
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Options Outstanding, Number of Shares Outstanding	1,665,565
Options Outstanding, Weighted-Average Remaining Contractual Life	6 years 6 months 15 days
Options Outstanding, Weighted-Average Exercise Price	$ 46.37
Options Exercisable, Number of Shares Outstanding	1,035,166
Options Exercisable, Weighted-Average Exercise Price	$ 34.52
$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	592,210
Options Outstanding, Weighted-Average Remaining Contractual Life	4 years 2 months 9 days
Options Outstanding, Weighted-Average Exercise Price	$ 26.50
Options Exercisable, Number of Shares Outstanding	589,210
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	487,968
Options Outstanding, Weighted-Average Remaining Contractual Life	6 years 10 months 28 days
Options Outstanding, Weighted-Average Exercise Price	$ 33.95
Options Exercisable, Number of Shares Outstanding	308,352
Options Exercisable, Weighted-Average Exercise Price	$ 34.00
$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	7 years 9 months 26 days
Options Outstanding, Weighted-Average Exercise Price	$ 66.58
Options Exercisable, Number of Shares Outstanding	118,089
Options Exercisable, Weighted-Average Exercise Price	$ 66.59
$79.90 - $ 93.56 [Member]
Share Based Compensation Shares Authorized Under Stock Option Plans Exercise Price Range [Line Items]
Range of Exercise Prices, Lower Range	$ 79.90
Range of Exercise Prices, Upper Range	$ 93.56
Options Outstanding, Number of Shares Outstanding	302,151
Options Outstanding, Weighted-Average Remaining Contractual Life	9 years 3 months 22 days
Options Outstanding, Weighted-Average Exercise Price	$ 86.42
Options Exercisable, Number of Shares Outstanding	19,515
Options Exercisable, Weighted-Average Exercise Price	$ 91.71