Summary Of Significant Accounting Policies (Calculation Of Basic And Diluted Earnings per Share) (Details) (USD $) In Thousands, except Share data	3 Months Ended								12 Months Ended
	Jul. 31, 2011	Apr. 30, 2011	Jan. 31, 2011	Oct. 31, 2010	Jul. 31, 2010	Apr. 30, 2010	Jan. 31, 2010	Oct. 31, 2009	Jul. 31, 2011	Jul. 31, 2010	Jul. 31, 2009
Summary Of Significant Accounting Policies
Weighted average shares - basic									77,196,370	77,848,528	77,967,141
Diluted share equivalents									1,402,000	1,329,000	1,233,000
Weighted average shares - diluted									78,598,459	79,177,772	79,199,838
Net earnings for basic and diluted earnings per share computation	$ 65,767	$ 61,811	$ 44,579	$ 53,134	$ 51,170	$ 49,458	$ 30,966	$ 34,569	$ 225,291	$ 166,163	$ 131,907
Net earnings per share - basic	$ 0.86	$ 0.80	$ 0.57	$ 0.69	$ 0.66	$ 0.64	$ 0.40	$ 0.44	$ 2.92	$ 2.13	$ 1.69
Net earnings per share - diluted	$ 0.84	$ 0.79	$ 0.56	$ 0.68	$ 0.65	$ 0.62	$ 0.39	$ 0.44	$ 2.87	$ 2.10	$ 1.67