Benefit Plans - Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Feb. 28, 2022	Feb. 28, 2021	Feb. 28, 2022	Feb. 28, 2021
Qualified Pension Benefits
Component of net periodic benefit costs: [Abstract]
Service cost	$ 11,569	$ 11,307	$ 23,138	$ 22,614
Interest cost	4,292	4,141	8,584	8,281
Expected return on assets	(10,990)	(10,910)	(21,979)	(21,821)
Prior service cost (credit) amortization	44	45	87	89
Actuarial loss (gain) amortization	5,852	5,447	11,703	10,895
Net periodic benefit cost (benefit)	10,767	10,030	21,533	20,058
Non-Qualified Pension Benefits
Component of net periodic benefit costs: [Abstract]
Service cost	232	108	463	217
Interest cost	70	68	141	136
Expected return on assets	0	0	0	0
Prior service cost (credit) amortization	(29)	(28)	(57)	(57)
Actuarial loss (gain) amortization	120	53	239	106
Net periodic benefit cost (benefit)	393	201	786	402
Other Benefits
Component of net periodic benefit costs: [Abstract]
Service cost	249	297	498	593
Interest cost	126	123	252	246
Expected return on assets	0	0	0	0
Prior service cost (credit) amortization	(111)	(111)	(223)	(223)
Actuarial loss (gain) amortization	(315)	(341)	(630)	(682)
Net periodic benefit cost (benefit)	$ (51)	$ (32)	$ (103)	$ (66)