Income Taxes (Components Of Income Tax Expense Attributable To Earnings) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Apr. 30, 2012	Apr. 30, 2011	Apr. 30, 2010
Income Taxes [Abstract]
Federal current tax expense	$ 9,937	$ (6,171)	$ 41,632
State current tax expense	2,345	1,871	4,794
Current income tax expense, total	12,282	(4,300)	46,426
Deferred income taxes	54,442	60,914	18,194
Total income tax provision	$ 66,724	$ 56,614	$ 64,620