Income Taxes (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended 6 Months Ended
Jan. 31, 2015
Jan. 31, 2014
Jan. 31, 2015
Jan. 31, 2014
Income Taxes [Abstract]        
Effective tax rate 27.00% 22.10% 27.30% 27.60%
Tax benefit associated with the favorable settlement of a tax audit   $ 6.4    
Unrecognized tax benefits 16.3   16.3  
Accrued interest and penalties on unrecognized tax benefits 1.7   1.7  
Statute of limitations period, average, years     5 years  
Maximum possible reduction in amount of unrecognized tax benefits     $ 1.0  
Unrecognized tax benefits potential expiration period     12 months