Pension and Other Postretirement Benefits (Details) - USD ($) $ in Thousands	3 Months Ended
	Oct. 31, 2018	Oct. 31, 2017
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	$ 422	$ 424
Interest cost	540	497
Expected return on plan assets	(702)	(486)
Amortization of Prior service costs	0	1
Amortization of Other actuarial loss	221	287
Net periodic benefit cost	481	723
Postretirement Health Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	27	29
Interest cost	25	24
Amortization of Prior service costs	(1)	(2)
Amortization of Other actuarial loss	0	5
Net periodic benefit cost	$ 51	$ 56