Benefit Plans - Components of Net Periodic Benefit Costa and Amounts Recognized in Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Aug. 31, 2023	Aug. 31, 2022	Aug. 31, 2021
Pension Benefits | Qualified Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Prior service cost	$ 490	$ 132	$ 113
Net actuarial loss (gain)	14,082	59,020	(4,408)
Amortization of actuarial (gain) loss	(1,872)	(23,406)	(21,790)
Amortization of prior service (credit) costs	(149)	(174)	(178)
Settlement of retiree obligations	0	0	0
Total recognized in other comprehensive loss (income)	12,551	35,572	(26,263)
Pension Benefits | Nonqualified Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Prior service cost	0	0	0
Net actuarial loss (gain)	1,282	(1,537)	1,978
Amortization of actuarial (gain) loss	(245)	(478)	(212)
Amortization of prior service (credit) costs	114	114	114
Settlement of retiree obligations	0	(307)	0
Total recognized in other comprehensive loss (income)	1,151	(2,208)	1,880
Other Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Prior service cost	0	0	0
Net actuarial loss (gain)	(1,865)	(4,243)	(1,163)
Amortization of actuarial (gain) loss	1,615	1,259	1,365
Amortization of prior service (credit) costs	445	445	445
Settlement of retiree obligations	0	0	0
Total recognized in other comprehensive loss (income)	$ 195	$ (2,539)	$ 647