Quarterly Financial Data (Schedule Of Share Price And Dividends Paid) (Details) (USD $)	3 Months Ended								12 Months Ended
	Apr. 30, 2012	Jan. 31, 2012	Oct. 31, 2011	Jul. 31, 2011	Apr. 30, 2011	Jan. 31, 2011	Oct. 31, 2010	Jul. 31, 2010	Apr. 30, 2012	Apr. 30, 2011
Quarterly Financial Data [Line Items]
Dividends paid per share	$ 0.20	$ 0.20	$ 0.15	$ 0.15	$ 0.15	$ 0.15	$ 0.15	$ 0.15	$ 0.70	$ 0.60
High [Member]
Quarterly Financial Data [Line Items]
Stock price range	$ 17.46	$ 17.09	$ 15.52	$ 17.75	$ 18.00	$ 13.79	$ 15.97	$ 18.99	$ 17.75	$ 18.99
Low [Member]
Quarterly Financial Data [Line Items]
Stock price range	$ 14.35	$ 14.41	$ 12.54	$ 14.68	$ 12.46	$ 11.15	$ 10.13	$ 13.44	$ 12.54	$ 10.13