Pension and Other Postretirement Benefits (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jan. 31, 2019	Jan. 31, 2018	Jan. 31, 2019	Jan. 31, 2018
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	$ 391	$ 438	$ 813	$ 862
Interest cost	517	517	1,057	1,014
Expected return on plan assets	(703)	(485)	(1,405)	(971)
Amortization of Prior service costs	1	0	1	1
Amortization of Other actuarial loss	165	354	386	641
Net periodic benefit cost	371	824	852	1,547
Postretirement Health Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	25	25	52	54
Interest cost	24	19	49	43
Amortization of Prior service costs	(2)	(1)	(3)	(3)
Amortization of Other actuarial loss	0	(5)	0	0
Net periodic benefit cost	$ 47	$ 38	$ 98	$ 94