Pension and Other Postretirement Benefits (Details) - USD ($) $ in Thousands	3 Months Ended
	Oct. 31, 2020	Oct. 31, 2019
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	$ 0	$ 488
Interest cost	0	509
Expected return on plan assets	0	(698)
Amortization of Other actuarial loss	170	357
Net periodic benefit cost	170	656
Postretirement Health Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	35	30
Interest cost	13	21
Amortization of Prior service costs	(1)	(1)
Net periodic benefit cost	$ 47	$ 50