Schedule I Parent Only Balance Sheets, Statements Of Earnings And Cash Flows (Parenthetical) (Details) (USD $) In Thousands, except Share data	12 Months Ended
	Jul. 31, 2011	Jul. 31, 2010	Jul. 31, 2009
Issuance costs	$ 300	$ 18	$ 401
Parent Company [Member]
Common unitholders, units outstanding	75,966,353	69,521,818
General partner unitholder, units outstanding	767,337	702,241
Issuance costs	$ 300	$ 18	$ 401