Pension and Other Postretirement Benefits (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Apr. 30, 2020	Apr. 30, 2019	Apr. 30, 2020	Apr. 30, 2019
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	$ 122	$ 407	$ 973	$ 1,220
Interest cost	444	529	1,456	1,586
Expected return on plan assets	(688)	(702)	(2,102)	(2,107)
Amortization of Prior service costs	0	0	0	1
Amortization of Other actuarial loss	167	192	837	578
Net periodic benefit cost	45	426	1,164	1,278
Postretirement Health Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	29	27	87	79
Interest cost	20	24	61	73
Amortization of Prior service costs	(2)	(2)	(5)	(5)
Net periodic benefit cost	$ 47	$ 49	$ 143	$ 147