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, 2022	Aug. 31, 2021	Aug. 31, 2020
Pension Benefits | Qualified Pension Benefits
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Prior service cost	$ 132	$ 113	$ 0
Net actuarial loss (gain)	59,020	(4,408)	3,401
Amortization of actuarial (gain) loss	(23,406)	(21,790)	(21,583)
Amortization of prior service (credit) costs	(174)	(178)	(178)
Settlement of retiree obligations	0	0	0
Total recognized in other comprehensive loss (income)	35,572	(26,263)	(18,360)
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)	(1,537)	1,978	2,157
Amortization of actuarial (gain) loss	(478)	(212)	(98)
Amortization of prior service (credit) costs	114	114	114
Settlement of retiree obligations	(307)	0	(397)
Total recognized in other comprehensive loss (income)	(2,208)	1,880	1,776
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)	(4,243)	(1,163)	(1,011)
Amortization of actuarial (gain) loss	1,259	1,365	1,392
Amortization of prior service (credit) costs	445	445	445
Settlement of retiree obligations	0	0	0
Total recognized in other comprehensive loss (income)	$ (2,539)	$ 647	$ 826