Contingent Liabilities And Commitments (Losses Due To Repurchases Under Repurchase Agreements) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jan. 31, 2012	Jan. 31, 2011	Jan. 31, 2012	Jan. 31, 2011
Contingent Liabilities And Commitments [Abstract]
Cost of units repurchased	$ 108	$ 2,848	$ 1,808	$ 5,068
Realization of units resold	55	2,400	1,582	4,327
Losses due to repurchase	$ 53	$ 448	$ 226	$ 741