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Stock Compensation Plan (Schedule Of Share Based Compensation Valuation Model) (Details)
12 Months Ended
Jul. 31, 2011
Jul. 31, 2010
Jul. 31, 2009
Stock Compensation Plan      
Expected volatility 42.50% 43.30%  
Expected volatility, minimum     37.10%
Expected volatility, maximum     41.00%
Expected dividends      
Expected term (average in years) 4.6 4.7  
Expected term (average in years), minimum     5.4
Expected term (average in years), maximum     5.7
Risk-free rate, minimum 0.30% 0.40% 2.10%
Risk-free rate, maximum 4.50% 4.60% 4.90%