Pension and Other Postretirement Benefits (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2016	Jan. 31, 2015
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	$ 267	$ 371	$ 756	$ 803
Interest cost	484	457	967	925
Expected return on plan assets	(485)	(469)	(962)	(939)
Amortization of Prior service costs	2	3	4	5
Amortization of Other actuarial loss	209	139	496	289
Net periodic benefit cost	477	501	1,261	1,083
Postretirement Health Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	21	34	43	67
Interest cost	21	26	41	53
Amortization of Prior service costs	(1)	(1)	(3)	(3)
Amortization of Other actuarial loss	0	9	0	18
Net periodic benefit cost	$ 41	$ 68	$ 81	$ 135