Benefit Plans - Net Periodic Benefit Cost (Details) - USD ($)	3 Months Ended
	Nov. 30, 2016	Nov. 30, 2015
Qualified Pension Benefits
Component of net periodic benefit costs: [Abstract]
Service cost	$ 9,383,000	$ 9,383,000
Interest cost	7,692,000	7,693,000
Expected return on assets	(12,014,000)	(12,014,000)
Prior service cost (credit) amortization	402,000	402,000
Actuarial (gain) loss amortization	4,765,000	4,754,000
Net periodic benefit cost	10,228,000	10,218,000
Defined Benefit Plan, Contributions by Employer	0
Non-Qualified Pension Benefits
Component of net periodic benefit costs: [Abstract]
Service cost	259,000	259,000
Interest cost	352,000	352,000
Expected return on assets	0	0
Prior service cost (credit) amortization	57,000	57,000
Actuarial (gain) loss amortization	173,000	173,000
Net periodic benefit cost	841,000	841,000
Other Benefits
Component of net periodic benefit costs: [Abstract]
Service cost	353,000	353,000
Interest cost	427,000	427,000
Expected return on assets	0	0
Prior service cost (credit) amortization	(30,000)	(30,000)
Actuarial (gain) loss amortization	(116,000)	(116,000)
Net periodic benefit cost	$ 634,000	$ 634,000