Contingent Liabilities And Commitments ( Losses Due To Repurchases Under Repurchase Agreements) (Details) (USD $) In Thousands	12 Months Ended
	Jul. 31, 2011	Jul. 31, 2010	Jul. 31, 2009
Contingent Liabilities And Commitments
Cost of units repurchased	$ 5,876	$ 10,001	$ 32,913
Realization of units resold	5,023	8,665	27,652
Losses due to repurchase	$ 853	$ 1,336	$ 5,261