Stockholders' Equity (Narrative) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Apr. 30, 2013	Apr. 30, 2012	Apr. 30, 2011
Schedule of Stockholders Equity [Line Items]
Shares repurchased and retired (in shares)	21,259,000	14,554,000	18,950,000
Share repurchase and retired, value	$ 315,000	$ 199,989	$ 279,947
Treasury stock retired	60,000,000
Preferred stock	500,000	500,000
Authorized unissued Preferred Stock	5,600,000
Preferred Stock No Par Value
Schedule of Stockholders Equity [Line Items]
Preferred stock	6,000,000
Participating Preferred Stock
Schedule of Stockholders Equity [Line Items]
Authorized unissued Preferred Stock	600,000
Convertible Preferred Stock
Schedule of Stockholders Equity [Line Items]
Preferred stock	500,000