Stock Option Activity (Detail) (USD $)	12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares, Outstanding Options at Beginning of Year	2,788,999	3,022,592	3,241,322
Number of Shares, Granted	297,151	256,989	569,679
Number of Shares, Exercised	(151,085)	(485,582)	(746,131)
Number of Shares, Cancelled	(1,269,500)	(5,000)	(42,278)
Number of Shares, Outstanding Options at End of Year	1,665,565	2,788,999	3,022,592
Number of Shares, Options Exercisable at End of Year	1,035,166	818,215	986,187
Weighted-Average Exercise Price, Outstanding Options at Beginning of year	$ 41.83	$ 37.83	$ 36.11
Weighted-Average Exercise Price, Granted	$ 86.41	$ 68.00	$ 34.64
Weighted-Average Exercise Price, Exercised	$ 32.38	$ 29.72	$ 27.64
Weighted-Average Exercise Price, Cancelled	$ 47.43	$ 53.22	$ 42.21
Weighted-Average Exercise Price, Outstanding Options at End of Year	$ 46.37	$ 41.83	$ 37.83
Weighted-Average Exercise Price, Weighted-Average Fair Value of Options Granted during the Year	$ 32.31	$ 26.35	$ 13.28