Retirement Plans (Schedules of Net Benefit Costs) (Details) - USD ($) $ in Thousands	12 Months Ended
	Aug. 31, 2020	Aug. 31, 2019	Aug. 31, 2018
Compensation And Retirement Disclosure [Abstract]
Interest cost	$ 208	$ 246	$ 243
Net amortization and deferral	226	199	206
Total	$ 434	$ 445	$ 449