Benefit Plans - Components of Net Periodic Benefit Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Aug. 31, 2023	Aug. 31, 2022	Aug. 31, 2021
experience study
Weighted-average assumptions to determine the net periodic benefit cost: [Abstract]
Actuarial (gain) loss	$ 0	$ 19
Other demographic experience
Weighted-average assumptions to determine the net periodic benefit cost: [Abstract]
Actuarial (gain) loss	(553)	717
Other Benefits
Component of net periodic benefit costs: [Abstract]
Service costs	670	996	$ 1,186
Expected return on assets	0	0	0
Amortization of actuarial (gain) loss	(1,615)	(1,259)	(1,365)
Periodic benefit costs, net	$ (355)	$ (205)	$ (131)
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate	4.64%	2.57%	2.43%
Weighted-average assumptions to determine the net periodic benefit cost: [Abstract]
Discount rate	5.33%	4.64%	2.57%
Amortization of prior service (credit) costs	$ (445)	$ (445)	$ (445)
Other Benefits | interest cost
Component of net periodic benefit costs: [Abstract]
Periodic benefit costs, net	1,035	503	493
Qualified Pension Benefits | experience study
Weighted-average assumptions to determine the net periodic benefit cost: [Abstract]
Actuarial (gain) loss	2,573	2,941
Qualified Pension Benefits | Other demographic experience
Weighted-average assumptions to determine the net periodic benefit cost: [Abstract]
Actuarial (gain) loss	5,181	9,875
Qualified Pension Benefits | Pension Benefits
Component of net periodic benefit costs: [Abstract]
Service costs	38,579	46,275	45,229
Amortization of actuarial (gain) loss	1,872	23,406	21,790
Periodic benefit costs, net	$ 28,059	$ 43,064	$ 40,119
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate	4.69%	2.80%	2.65%
Expected return on plan assets	4.88%	4.88%	4.90%
Rate of compensation increase	4.93%	4.79%	4.99%
Weighted-average assumptions to determine the net periodic benefit cost: [Abstract]
Discount rate	5.38%	4.69%	2.78%
Rate of compensation increase	4.98%	4.93%	4.79%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Weighted-Average Interest Crediting Rate	4.80%	4.65%	4.65%
Amortization of prior service (credit) costs	$ 149	$ 174	$ 178
Qualified Pension Benefits | Pension Benefits | interest cost
Component of net periodic benefit costs: [Abstract]
Periodic benefit costs, net	30,588	17,167	16,563
Qualified Pension Benefits | Pension Benefits | expected return on asset
Component of net periodic benefit costs: [Abstract]
Periodic benefit costs, net	(43,129)	(43,958)	(43,641)
Nonqualified Pension Benefits | experience study
Weighted-average assumptions to determine the net periodic benefit cost: [Abstract]
Actuarial (gain) loss	159	43
Nonqualified Pension Benefits | Other demographic experience
Weighted-average assumptions to determine the net periodic benefit cost: [Abstract]
Actuarial (gain) loss	1,999	1,313
Nonqualified Pension Benefits | Pension Benefits
Component of net periodic benefit costs: [Abstract]
Service costs	1,840	926	433
Expected return on assets	0	0	0
Amortization of actuarial (gain) loss	245	478	212
Periodic benefit costs, net	$ 2,712	$ 1,571	$ 804
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate	4.48%	2.04%	2.07%
Rate of compensation increase	4.93%	4.79%	4.99%
Weighted-average assumptions to determine the net periodic benefit cost: [Abstract]
Discount rate	5.23%	4.49%	2.08%
Rate of compensation increase	4.98%	4.93%	4.79%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Weighted-Average Interest Crediting Rate	4.80%	4.65%	4.65%
Amortization of prior service (credit) costs	$ (114)	$ (114)	$ (114)
Nonqualified Pension Benefits | Pension Benefits | interest cost
Component of net periodic benefit costs: [Abstract]
Periodic benefit costs, net	$ 741	$ 281	$ 273