Pension and Other Postretirement Benefits (Details) - USD ($) $ in Thousands	3 Months Ended
	Oct. 31, 2015	Oct. 31, 2014
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	$ 489	$ 432
Interest cost	483	468
Expected return on plan assets	(477)	(470)
Amortization of Prior service costs	2	2
Amortization of Other actuarial loss	287	150
Net periodic benefit cost	784	582
Postretirement Health Plan
Defined Benefit Plans and Other Postretirement Benefit Plans
Service cost	22	33
Interest cost	20	27
Amortization of Prior service costs	(2)	(2)
Amortization of Other actuarial loss	0	9
Net periodic benefit cost	$ 40	$ 67