Pension and Postretirement Benefit Plans (Details) - USD ($) $ in Thousands	3 Months Ended
	Nov. 30, 2015	Nov. 30, 2014
Pension Plans, Defined Benefit [Member]
Defined Benefit Pension Plan Disclosure [Line Items]
Service cost	$ 1,294	$ 1,254
Interest cost	1,063	1,168
Expected return on plan assets	(504)	(471)
Actuarial loss (gain) and amortization of prior service cost (credit), net	724	786
Net periodic benefit cost	2,577	2,737
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Pension Plan Disclosure [Line Items]
Service cost	1	1
Interest cost	97	110
Actuarial loss (gain) and amortization of prior service cost (credit), net	(149)	(135)
Net periodic benefit cost	$ (51)	$ (24)