Benefit Plans - Net Periodic Benefit Cost (Details) - USD ($)	3 Months Ended
Nov. 30, 2017	Nov. 30, 2016
Qualified Pension Benefits
Component of net periodic benefit costs: [Abstract]
Service cost	$ 9,919,000	$ 9,383,000
Interest cost	6,002,000	7,692,000
Expected return on assets	(12,040,000)	(12,014,000)
Prior service cost (credit) amortization	359,000	402,000
Actuarial (gain) loss amortization	6,888,000	4,765,000
Net periodic benefit cost	11,128,000	10,228,000
Defined Benefit Plan, Plan Assets, Contributions by Employer	0
Non-Qualified Pension Benefits
Component of net periodic benefit costs: [Abstract]
Service cost	137,000	259,000
Interest cost	178,000	352,000
Expected return on assets	0	0
Prior service cost (credit) amortization	8,000	57,000
Actuarial (gain) loss amortization	15,000	173,000
Net periodic benefit cost	338,000	841,000
Other Benefits
Component of net periodic benefit costs: [Abstract]
Service cost	236,000	353,000
Interest cost	227,000	427,000
Expected return on assets	0	0
Prior service cost (credit) amortization	(141,000)	(30,000)
Actuarial (gain) loss amortization	(306,000)	(116,000)
Net periodic benefit cost	$ 16,000	$ 634,000

Amount of gain (loss) recognized in net periodic benefit (cost) credit of defined benefit plan.

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- Definition

Amount of prior service cost (credit) recognized in net periodic benefit cost (credit) of defined benefit plan.

+ References

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- Definition

Amount of contribution received by defined benefit plan from employer which increases plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(5)(ii)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e2709-114920

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(5)(iv)(01)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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- Definition

Amount of expected return (loss) recognized in net periodic benefit (cost) credit, calculated based on expected long-term rate of return and market-related value of plan assets of defined benefit plan.

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- Definition

Amount of cost recognized for passage of time related to defined benefit plan.

+ References

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- Definition

Amount of net periodic benefit cost (credit) for defined benefit plan.

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No definition available.

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- Definition

Amount of cost for actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

+ References

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