Commitments And Contingencies (Rollforward Of Reserve For Losses On Repurchases) (Details) (USD $) In Thousands	3 Months Ended
	Jul. 31, 2011	Jul. 31, 2010	Apr. 30, 2009	Jul. 31, 2011 Repurchase And Indemnifications [Member]	Apr. 30, 2011 Repurchase And Indemnifications [Member]	Jul. 31, 2010 Repurchase And Indemnifications [Member]	Apr. 30, 2009 Repurchase And Indemnifications [Member]	Jul. 31, 2011 Indemnity Agreement Dated April 2008 [Member]	Apr. 30, 2011 Indemnity Agreement Dated April 2008 [Member]	Jul. 31, 2010 Indemnity Agreement Dated April 2008 [Member]	Apr. 30, 2009 Indemnity Agreement Dated April 2008 [Member]
Reserve for losses on repurchases, beginning balance	$ 126,260		$ 188,200	$ 125,775	$ 126,260	$ 138,415	$ 138,415			$ 49,715	$ 49,785
Provisions
Losses on repurchase and indemnifications	(485)
Payments under indemnity agreement dated April 2008		(70)
Reserve for losses on repurchases, ending balance	$ 125,775	$ 188,130	$ 188,200	$ 125,775	$ 126,260	$ 138,415	$ 138,415			$ 49,715	$ 49,785