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Benefit Plans (Details) - USD ($)
$ in Millions
12 Months Ended
Jul. 31, 2020
Jul. 31, 2019
Jul. 31, 2018
Retirement Benefits [Abstract]      
Maximum percent of salary and bonus eligible for executive deferred compensation plan 75.00%    
Executive deferred compensation plan liabilities $ 123 $ 108  
Maximum percent of pre tax salary eligible for contribution to employee plan 50.00%    
Additional employer contribution for next six percent of salary (in percent) 125.00%    
Additional salary contributed by the employee (in percent) 6.00%    
Matching contributions $ 69 $ 59 $ 50