Benefit Plans - Net Periodic Benefit Cost (Details) - USD ($)	3 Months Ended	6 Months Ended
Feb. 29, 2016	Feb. 28, 2015	Feb. 29, 2016	Feb. 28, 2015
Qualified Pension Benefits
Component of net periodic benefit costs: [Abstract]
Service costs	$ 9,383,000	$ 9,058,000	$ 18,766,000	$ 18,116,000
Interest costs	7,691,000	7,002,000	15,384,000	14,016,000
Expected return on assets	(12,013,000)	(12,436,000)	(24,027,000)	(24,874,000)
Prior service cost (credit) amortization	401,000	409,000	803,000	816,000
Actuarial loss (gain) amortization	4,775,000	4,907,000	9,529,000	9,808,000
Periodic benefit costs, net	10,237,000	8,940,000	20,455,000	17,882,000
Defined Benefit Plan, Contributions by Employer			0
Non-Qualified Pension Benefits
Component of net periodic benefit costs: [Abstract]
Service costs	259,000	225,000	518,000	450,000
Interest costs	351,000	352,000	703,000	704,000
Expected return on assets	0	0	0	0
Prior service cost (credit) amortization	57,000	57,000	114,000	114,000
Actuarial loss (gain) amortization	173,000	261,000	346,000	522,000
Periodic benefit costs, net	840,000	895,000	1,681,000	1,790,000
Other Benefits
Component of net periodic benefit costs: [Abstract]
Service costs	353,000	474,000	706,000	946,000
Interest costs	428,000	415,000	855,000	830,000
Expected return on assets	0	0	0	0
Prior service cost (credit) amortization	(30,000)	(30,000)	(60,000)	(60,000)
Actuarial loss (gain) amortization	(116,000)	(106,000)	(232,000)	(211,000)
Periodic benefit costs, net	$ 635,000	$ 753,000	$ 1,269,000	$ 1,505,000

The amount of gains or losses recognized in net periodic benefit cost.

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- Definition

The amount of the prior service cost or credit recognized in net periodic benefit cost relating to benefit changes attributable to plan participants' prior service pursuant to a plan amendment or a plan initiation.

+ 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 (h)(1)
-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Prior Service Cost
-URI http://asc.fasb.org/extlink&oid=49177896

+ Details

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- Definition

The increase in the fair value of plan assets from contributions made by the employer.

+ References

+ Details

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- Definition

An amount calculated as a basis for determining the extent of delayed recognition of the effects of changes in the fair value of assets. The expected return on plan assets is determined based on the expected long-term rate of return on plan assets and the market-related value of plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Expected Return on Plan Assets
-URI http://asc.fasb.org/extlink&oid=6512171

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (h)(3)
-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920

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- Definition

The increase in a defined benefit pension plan's projected benefit obligation or a defined benefit postretirement plan's accumulated postretirement benefit obligation due to the passage of time.

+ 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 (h)(2)
-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920

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-Publisher FASB
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-Section 50
-Paragraph 1
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920

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- Definition

The total amount of net periodic benefit cost for defined benefit plans for the period. Periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) due to settlements or curtailments.

+ 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 (h)
-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920

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- References

No definition available.

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- Definition

The actuarial present value of benefits attributed by the pension benefit formula to services rendered by employees during the period. The portion of the expected postretirement benefit obligation attributed to employee service during the period. The service cost component is a portion of the benefit obligation and is unaffected by the funded status of the plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Service Cost (Component of Net Periodic Pension Cost)
-URI http://asc.fasb.org/extlink&oid=6525008

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (h)(1)
-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920

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-Publisher FASB
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-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920

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