Treasury Stock (Details) (USD $)	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Summary of share repurchases and cumulatively since inception of authorization
Shares repurchased	705,406	461,938	715,975
Shares repurchased, Cumulative	15,658,507	14,953,101
Cost	$ 30,727,000	$ 21,643,000	$ 30,608,000
Cost, Cumulative	$ 301,301,000	$ 270,574,000
Average price	$ 43.56	$ 46.85	$ 42.75
Average price, Cumulative	$ 19.24