Schedule of Stock Option Activity (Detail) (USD $)	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Stock Option Activity And Changes [Line Items]
Outstanding at beginning of year, Options	189,345	408,850	474,670
Granted, Options
Exercised, Options
Forfeited, Options	(69,000)	(219,505)	(65,820)
Outstanding at end of year, Options	120,345	189,345	408,850
Options vested and exercisable at year-end, Options	120,345	189,345	408,850
Intrinsic value of options exercised, Options
Outstanding at beginning of year, Weighted Average Price	$ 25.19	$ 22.34	$ 21.61
Granted, Weighted Average Price
Exercised, Weighted Average Price
Forfeited, Weighted Average Price	$ 24.08	$ 19.89	$ 17.08
Outstanding at end of year, Weighted Average Price	$ 25.82	$ 25.19	$ 22.34
Options vested and exercisable at year-end, Weighted Average Price	$ 25.82	$ 25.19	$ 22.34
Intrinsic value of options exercised, Weighted Average Price