Pension and Other Postretirement Benefits Assumptions (Details)
9 Months Ended
Apr. 30, 2013
Apr. 30, 2012
Pension Plan
   
Defined Benefit Plans and Other Postretirement Benefit Plans    
Discount rate for net periodic benefit cost 3.75% 5.25%
Rate of increase in compensation levels 3.50% 4.00%
Long-term expected rate of return on assets 7.50% 7.50%
Postretirement Health Plan
   
Defined Benefit Plans and Other Postretirement Benefit Plans    
Discount rate for net periodic benefit cost 3.75% 5.25%
Rate of increase in compensation levels 0.00% 0.00%
Long-term expected rate of return on assets 0.00% 0.00%