Stockholders' Equity (Narrative) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	1 Months Ended	3 Months Ended	12 Months Ended
	Jun. 30, 2012	Jul. 31, 2012	Apr. 30, 2012	Apr. 30, 2011	Apr. 30, 2010
Schedule of Stockholders Equity [Line Items]
Shares repurchased and retired		21,300,000	14,554,000	18,950,000	12,786,000
Share repurchase and retired, value		$ 315,000	$ 199,989	$ 279,947	$ 250,003
Treasury stock retired	60,000,000
Preferred stock			500,000	500,000
Authorized unissued Preferred Stock			5,600,000
Convertible Preferred Stock [Member]
Schedule of Stockholders Equity [Line Items]
Preferred stock			500,000
Preferred Stock No Par Value [Member]
Schedule of Stockholders Equity [Line Items]
Preferred stock			6,000,000
Participating Preferred Stock [Member]
Schedule of Stockholders Equity [Line Items]
Authorized unissued Preferred Stock			600,000