Net Earnings (Loss) Per Common Unitholders' Interest (Basic And Diluted Net Earnings Per Common Unitholders' Interest) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jan. 31, 2012	Jan. 31, 2011	Jan. 31, 2012	Jan. 31, 2011
Net Earnings (Loss) Per Common Unitholders' Interest [Abstract]
Common unitholders' interest in net earnings (loss)	$ 36,010	$ 21,908	$ 3,732	$ (5,855)
Weighted average common units outstanding	76,401,600	70,668,800	76,184,000	70,114,200
Dilutive securities	62,200	131,300	65,100	0
Weighted average common units outstanding plus dilutive securities	76,463,800	70,800,100	76,249,100	70,114,200
Basic and diluted net earnings (loss) per common unitholders' interest	$ 0.47	$ 0.31	$ 0.05	$ (0.08)