Loss Per Share And Stockholders' Equity (Allocation Of Cost Of Shares Retired To Components Of Stockholders' Equity) (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Jan. 31, 2013	Jan. 31, 2012
Earnings Per Share And Equity [Line Items]
Cost of common shares retired	$ 315,000	$ 177,504
Cost of treasury shares retired	1,140,797
Net impact on consolidated stockholders' equity
Common Stock [Member]
Earnings Per Share And Equity [Line Items]
Cost of common shares retired	213	130
Cost of treasury shares retired	600
Additional Paid-in Capital [Member]
Earnings Per Share And Equity [Line Items]
Cost of common shares retired	12,542	7,826
Cost of treasury shares retired	35,400
Retained Earnings [Member]
Earnings Per Share And Equity [Line Items]
Cost of common shares retired	302,245	169,548
Cost of treasury shares retired	$ 1,104,797