Stockholder's Investment (Details Textual) (USD $)	12 Months Ended				12 Months Ended								1 Months Ended	12 Months Ended	1 Months Ended	12 Months Ended
	Jul. 31, 2011	Jul. 31, 2010	Jul. 31, 2009	Jul. 31, 2008	Jul. 31, 2011 Common Class A [Member]	Jul. 31, 2010 Common Class A [Member]	Jul. 31, 2009 Common Class A [Member]	Jul. 31, 2008 Common Class A [Member]	Jul. 31, 2011 Class B Common Stock [Member]	Jul. 31, 2011 Class A nonvoting common stock [Member]	Jul. 31, 2011 Service Based Options [Member]	Jul. 31, 2011 Performance Based [Member]	Aug. 31, 2010 Frank M. Jaehnert Performance Based Restricted Shares [Member]	Jul. 31, 2011 Frank M. Jaehnert Performance Based Restricted Shares [Member]	Aug. 31, 2010 Performance Based Restricted Shares [Member]	Jul. 31, 2011 Performance Based Restricted Shares [Member]	Jul. 31, 2008 Performance Based Restricted Shares [Member]	Jul. 31, 2011 Performance Based Options [Member]	Jul. 31, 2010 Performance Based Options [Member]	Jul. 31, 2011 Service Based Option [Member]	Jul. 31, 2011 Frank M. Jaehnert	Jul. 31, 2011 Thomas J. Felmer	Jul. 31, 2011 Robert L.Tatterson	Jul. 31, 2010 Robert L.Tatterson	Jul. 31, 2011 Peter C. Sephton	Jul. 31, 2011 Matthew O. Williamson
Class of Stock [Line Items]
Noncumulative cash dividend					0.01665
Amount of per share dividend entitled to common stock holders after distribution of Cumulative Preferred Stock holders in case of liquidation, dissolution or winding up of the Company					0.835				$ 0.835
Shares reacquired in connection with its repurchase plan						102,067	1,345,000	1,349,000
Value of reacquired shares in connection with its repurchase plan						$ 2,500,000	$ 40,300,000	$ 42,200,000
Remained Shares to repurchase in connection with its repurchase plan					204,133
Stock option vest ratably period										Generally vest ratably over a three-year period, with one-third becoming exercisable one year after the grant date and one-third additional in each of the succeeding two years
Outstanding stock options and restricted shares of Class A Nonvoting Common Stock										5,799,017
Future issuance of stock options and restricted shares of Class A Nonvoting Common Stock remain										737,000
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award expiring period from grant date											10 years	10years				five-year or seven-year
Outstanding stock options and restricted shares of Class A Nonvoting Common Stock	5,726,017	5,108,736	3,980,606	3,985,205
Share-based compensation expense																1,200,000
Weighted-average fair value of options granted																$ 28.35		9.87	8.70	9.59
Weighted-average exercise price																$ 28.35		28.35	29.78	29.13
Performance-based restricted shares													100,000	100,000			210,000	465,000		900,500
Grant price and fair value of restricted shares															28.35		32.83
Performance-based restricted shares outstanding																310,000
Stockholder's Investment Investment (Textuals) [Abstract]
Employees authorized to deduct pay monthly Under employee monthly stock investment plan, minimum	20
Employees authorized to deduct pay monthly Under employee monthly stock investment plan, maximum	500
Total fair value of options vested	6,822,000	5,548,000	6,559,000
Total intrinsic value of options exercised	5,701,000	3,004,000	2,156,000
Exercisable Performance Based Stock Options	3,316,815	3,100,955	2,831,311																		50,000	35,000	20,000	20,000	35,000	35,000
Weighted average exercise price	$ 29.83	$ 28.85	$ 27.46
Proceeds from issuance of common stock	8,193,000	3,717,000	1,683,000
Tax benefit on options exercised	682,000	866,000	779,000
Aggregate intrinsic value of the number of options outstanding	14,864,000
Aggregate intrinsic value of the number of options exercisable	$ 11,727,000