Benefit Plans - Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Nov. 30, 2021	Nov. 30, 2020
Qualified Pension Benefits
Component of net periodic benefit costs: [Abstract]
Service cost	$ 11,569	$ 11,307
Interest cost	4,292	4,141
Expected return on assets	(10,990)	(10,910)
Prior service cost (credit) amortization	44	45
Actuarial loss (gain) amortization	5,852	5,447
Net periodic benefit cost (benefit)	10,767	10,030
Non-Qualified Pension Benefits
Component of net periodic benefit costs: [Abstract]
Service cost	232	108
Interest cost	70	68
Expected return on assets	0	0
Prior service cost (credit) amortization	(29)	(28)
Actuarial loss (gain) amortization	120	53
Net periodic benefit cost (benefit)	393	201
Other Benefits
Component of net periodic benefit costs: [Abstract]
Service cost	249	297
Interest cost	126	123
Expected return on assets	0	0
Prior service cost (credit) amortization	(111)	(111)
Actuarial loss (gain) amortization	(315)	(341)
Net periodic benefit cost (benefit)	$ (51)	$ (32)