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Summary Of Significant Accounting Policies (Summary Of Estimated Fair Value Of Financial Instruments) (Details) (USD $)
In Thousands, unless otherwise specified
Jan. 31, 2012
Jul. 31, 2011
Jan. 31, 2011
Debt Instrument [Line Items]      
Carrying Value $ 491,360 $ 491,743 $ 497,757
6.50% Notes [Member]
     
Debt Instrument [Line Items]      
Carrying Value 390,000 390,000  
Fair Value 401,700    
Industrial Development Bonds [Member]
     
Debt Instrument [Line Items]      
Carrying Value 41,200 41,200 41,200
Fair Value 47,340    
Other Long-Term Debt [Member]
     
Debt Instrument [Line Items]      
Carrying Value 7,585    
Fair Value $ 7,867