Benefit Plans - Net Periodic Benefit Cost (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
May 31, 2014	May 31, 2013	May 31, 2014	May 31, 2013
Qualified Pension Benefits
Component of net periodic benefit costs: [Abstract]
Service costs	$ 7,543	$ 9,109	$ 22,812	$ 23,541
Interest costs	7,495	6,072	22,433	19,078
Expected return on assets	(11,910)	(13,388)	(35,726)	(37,311)
Prior service cost (credit) amortization	398	399	1,195	1,198
Actuarial loss (gain) amortization	4,566	6,500	13,655	16,961
Transition amount amortization	0	0	0	0
Periodic benefit costs, net	8,092	8,692	24,369	23,467
Defined Benefit Plan, Contributions by Employer			0
Non-Qualified Pension Benefits
Component of net periodic benefit costs: [Abstract]
Service costs	219	211	646	540
Interest costs	423	340	1,245	987
Expected return on assets	0	0	0	0
Prior service cost (credit) amortization	57	57	171	171
Actuarial loss (gain) amortization	250	270	718	692
Transition amount amortization	0	0	0	0
Periodic benefit costs, net	949	878	2,780	2,390
Other Benefits
Component of net periodic benefit costs: [Abstract]
Service costs	339	935	1,297	2,202
Interest costs	418	443	1,439	1,675
Expected return on assets	0	0	0	0
Prior service cost (credit) amortization	(30)	(81)	(90)	(90)
Actuarial loss (gain) amortization	(228)	371	(415)	817
Transition amount amortization	0	73	0	422
Periodic benefit costs, net	$ 499	$ 1,741	$ 2,231	$ 5,026

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.

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+ Details

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- Definition

The amount of the transition obligation or asset recognized in net periodic benefit cost.

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+ Details

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- Definition

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

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+ 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

-Topic 715

-SubTopic 30

-Glossary Expected Return on Plan Assets

-URI http://asc.fasb.org/extlink&oid=6512136

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 60

-Glossary Expected Return on Plan Assets

-URI http://asc.fasb.org/extlink&oid=6512171

Reference 3: 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=28361610&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.

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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.

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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

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (h)(1)

-URI http://asc.fasb.org/extlink&oid=28361610&loc=d3e1928-114920

Reference 2: 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 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=28361610&loc=d3e1928-114920

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