Employee Benefit Plans - Schedule of Assumptions Used (Details)	12 Months Ended
	Jul. 31, 2017 Rate	Jul. 31, 2016 Rate	Jul. 31, 2015 Rate
Compensation and Retirement Disclosure [Abstract]
Weighted average discount rate used in determining accumulated postretirement benefit obligation	2.50%	2.50%	3.00%
Weighted average discount rate used in determining net periodic benefit cost	2.50%	3.00%	3.41%
Assumed health care trend rate used to measure accumulated postretirement benefit obligation at July 31	7.25%	7.50%	7.00%
Rate to which cost trend rate is assumed to decline (the ultimate trend rate)	5.50%	5.50%	5.50%
Fiscal year the ultimate trend rate is reached	2024	2018	2018