Benefits and Pension Plans - Weighted Average Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Aug. 31, 2022	Aug. 31, 2021	Aug. 31, 2020
Weighted-average assumptions used to determine benefit obligations
Rate of compensation increase (as a percent)	3.50%	3.50%	3.50%
Weighted-average assumptions used to determine net periodic benefit cost
Rate of compensation increase (as a percent)	3.50%	3.50%	3.50%
Qualified Plan.
Weighted-average assumptions used to determine benefit obligations
Discount rate (as a percent)	4.21%	2.15%	1.92%
Weighted-average assumptions used to determine net periodic benefit cost
Discount rate (as a percent)	2.15%	1.92%	2.58%
Expected long term return on plan assets (as a percent)	4.85%	5.25%	5.60%
Reduction in discount rate used to estimate additional net periodic pension cost (as a percent)	1.00%
Additional net periodic pension cost from each 100 basis point reduction in the discount rate	$ 37
Reduction in expected return on plan assets used to estimate the increase in net periodic pension cost (as a percent)	1.00%
Additional net periodic pension cost from each 100 basis point reduction in the expected return on plan assets	$ 85
Supplemental plan
Weighted-average assumptions used to determine benefit obligations
Discount rate (as a percent)	4.36%	1.95%	1.65%
Weighted-average assumptions used to determine net periodic benefit cost
Discount rate (as a percent)	1.95%	1.65%	2.37%
Additional net periodic pension cost from each 100 basis point reduction in the discount rate	$ (35)
NEPTCO | Qualified Plan.
Weighted-average assumptions used to determine net periodic benefit cost
Discount rate (as a percent)			2.29%
Expected long term return on plan assets (as a percent)			5.60%