Quarterly Financial Data (Schedule Of Share Price And Dividends Paid) (Details) (USD $)	3 Months Ended								12 Months Ended
	Apr. 30, 2013	Jan. 31, 2013	Oct. 31, 2012	Jul. 31, 2012	Apr. 30, 2012	Jan. 31, 2012	Oct. 31, 2011	Jul. 31, 2011	Apr. 30, 2013	Apr. 30, 2012
Quarterly Financial Data [Line Items]
Dividends paid per share	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.15	$ 0.15	$ 0.80	$ 0.70
High
Quarterly Financial Data [Line Items]
Stock price range	$ 29.68	$ 23.19	$ 18.04	$ 16.88	$ 17.46	$ 17.09	$ 15.52	$ 17.75	$ 29.68	$ 17.75
Low
Quarterly Financial Data [Line Items]
Stock price range	$ 22.77	$ 17.26	$ 15.53	$ 14.35	$ 14.35	$ 14.41	$ 12.54	$ 14.68	$ 14.35	$ 12.54