Investments And Fair Value Measurements (Tables)
 9 Months Ended
Apr. 30, 2012
Investments And Fair Value Measurements [Abstract]  
Financial Assets Measured At Fair Value On Recurring Basis
    April 30, 2012     July 31, 2011  
        Cash and Cash    
Equivalents		         Auction Rate    
Securities		         Cash and Cash    
Equivalents		         Auction Rate    
Securities		  

Levels of Input:                

        

Level 1

       $ 147,986          $ –          $ 215,435          $ –   

Level 2

     –        –        –        –   

Level 3

     –        1,636        –        2,042   
 

 

 

    

 

 

    

 

 

    

 

 

  
      $ 147,986          $ 1,636          $ 215,435          $ 2,042   
 

 

 

    

 

 

    

 

 

    

 

 

  
Assets Measured At Fair Value Using Significant Unobservable Inputs
     Fair Value Measurements at
Reporting Date Using
Significant Unobservable
Inputs
(Level 3)		  

Balances at July 31, 2011

          $ 2,042    

 Net change in other comprehensive income

      (6)    

 Net loss included in earnings

      –    

 Purchases

      –    

 Sales/Maturities

      (400)    
  

 

 

  

Balances at April 30, 2012

          $ 1,636