Commitments And Contingencies (Rollforward Of Reserve For Losses On Repurchases) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
	Oct. 31, 2011	Oct. 31, 2011	Oct. 31, 2010	Jul. 31, 2010	Jul. 31, 2011 Repurchase And Indemnifications [Member]	Jul. 31, 2010 Repurchase And Indemnifications [Member]	Oct. 31, 2011 Indemnity Agreement Dated April 2008 [Member]	Oct. 31, 2010 Indemnity Agreement Dated April 2008 [Member]	Jul. 31, 2010 Indemnity Agreement Dated April 2008 [Member]
Reserve for losses on repurchases, beginning balance	$ 126,260			$ 188,200	$ 126,260	$ 138,415	$ 142,923	$ 135,071	$ 49,785
Provisions		20,000
Losses on repurchase and indemnifications		(3,337)	(3,344)
Payments under indemnity agreement	49,800		(134)
Reserve for losses on repurchases, ending balance			$ 49,651	$ 188,200	$ 126,260	$ 138,415	$ 142,923	$ 135,071	$ 49,785