Pension and Postretirement Benefit Plans (Details) - Pension Plans, Defined Benefit [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Feb. 28, 2018	Feb. 28, 2017	Feb. 28, 2018	Feb. 28, 2017
Defined Benefit Pension Plan Disclosure [Line Items]
Service cost	$ 1,342	$ 1,344	$ 2,640	$ 2,739
Interest cost	796	570	1,567	1,157
Expected return on plan assets	(410)	(367)	(806)	(743)
Amortization of actuarial loss (gain)	724	961	1,424	1,958
Net periodic pension benefit cost	$ 2,452	$ 2,508	$ 4,825	$ 5,111