Benefit Plans - Net Periodic Benefit Cost (Details) - USD ($)	3 Months Ended
	Nov. 30, 2018	Nov. 30, 2017
Qualified Pension Benefits
Component of net periodic benefit costs: [Abstract]
Service cost	$ 9,648,000	$ 9,919,000
Interest cost	7,099,000	6,002,000
Expected return on assets	(11,242,000)	(12,040,000)
Prior service cost (credit) amortization	42,000	359,000
Actuarial (gain) loss amortization	3,087,000	4,518,000
Net periodic benefit cost	8,634,000	8,758,000
Defined Benefit Plan, Plan Assets, Contributions by Employer	0
Non-Qualified Pension Benefits
Component of net periodic benefit costs: [Abstract]
Service cost	78,000	137,000
Interest cost	187,000	178,000
Expected return on assets	0	0
Prior service cost (credit) amortization	(19,000)	8,000
Actuarial (gain) loss amortization	0	15,000
Net periodic benefit cost	246,000	338,000
Other Benefits
Component of net periodic benefit costs: [Abstract]
Service cost	263,000	236,000
Interest cost	274,000	227,000
Expected return on assets	0	0
Prior service cost (credit) amortization	(139,000)	(141,000)
Actuarial (gain) loss amortization	(407,000)	(306,000)
Net periodic benefit cost	$ (9,000)	$ 16,000