Benefit Plans - Rollforward of Benefit Obligation and Plan Assets Funded (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Aug. 31, 2014	Aug. 31, 2013	Aug. 31, 2012
Qualified Pension Benefits
Component of net periodic benefit costs: [Abstract]
Service costs	$ 30,417	$ 31,387	$ 26,010
Interest costs	29,900	25,445	24,119
Expected return on assets	(47,655)	(49,728)	(40,904)
Settlement of retiree obligations	0	0	0
Prior service cost (credit) amortization	1,593	1,597	1,831
Actuarial loss (gain) amortization	18,228	22,615	15,131
Transition amount amortization	0	0	0
Periodic benefit costs, net	32,483	31,316	26,187
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate	4.80%	3.80%	5.00%
Expected return on plan assets	6.75%	7.25%	7.25%
Rate of compensation increase	4.85%	4.50%	4.50%
Weighted-average assumptions to determine the net periodic benefit cost: [Abstract]
Discount rate	4.00%	4.80%	3.80%
Rate of compensation increase	4.90%	4.85%	4.50%
Non-Qualified Pension Benefits
Component of net periodic benefit costs: [Abstract]
Service costs	860	721	279
Interest costs	1,660	1,316	1,343
Expected return on assets	0	0	0
Settlement of retiree obligations	0	0	0
Prior service cost (credit) amortization	229	228	228
Actuarial loss (gain) amortization	957	921	428
Transition amount amortization	0	0	0
Periodic benefit costs, net	3,706	3,186	2,278
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate	4.50%	4.25%	5.00%
Rate of compensation increase	4.75%	4.75%	4.75%
Weighted-average assumptions to determine the net periodic benefit cost: [Abstract]
Discount rate	4.50%	4.50%	4.00%
Rate of compensation increase	4.80%	4.75%	4.75%
Other Benefits
Component of net periodic benefit costs: [Abstract]
Service costs	1,729	2,936	2,556
Interest costs	1,918	2,275	2,638
Expected return on assets	0	0	0
Settlement of retiree obligations	0	0	0
Prior service cost (credit) amortization	(493)	(120)	(104)
Actuarial loss (gain) amortization	(180)	1,104	891
Transition amount amortization	0	562	936
Periodic benefit costs, net	$ 2,974	$ 6,757	$ 6,917
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract]
Discount rate	3.75%	3.75%	4.75%
Rate of compensation increase	4.50%	4.50%	4.50%
Weighted-average assumptions to determine the net periodic benefit cost: [Abstract]
Discount rate	4.60%	3.75%	3.75%
Rate of compensation increase	4.50%	4.50%	4.50%

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

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- Definition

The interest rate used to adjust for the time value of money for the plan.

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- Definition

Expected rate of compensation increases (for pay-related plans).

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- Definition

The interest rate used to adjust for the time value of money.

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- Definition

An assumption as to the rate of return on plan assets reflecting the average rate of earnings expected on the funds invested or to be invested to provide for the benefits included in the benefit obligation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 30

-Glossary Expected Long-Term Rate of Return on Plan Assets

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (k)(3)

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- Definition

Expected rate of compensation increases (for pay-related plans).

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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

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 60

-Glossary Expected Return on Plan Assets

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

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (h)(3)

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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

Amount of net gain (loss) recognized in net periodic benefit cost as a result of an irrevocable action that relieves the employer (or the plan) of primary responsibility for a benefit obligation and eliminates significant risks related to the obligation and the assets used to effect the settlement. Examples of transactions that constitute a settlement include, but are not limited to, lump-sum cash payments to plan participants in exchange for their rights to receive specified benefits and purchasing nonparticipating annuity contracts to cover vested benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 30

-Section 15

-Paragraph 6

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=7577095&loc=d3e8001-114927

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (h)(7)

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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)

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-Publisher FASB

-Name Accounting Standards Codification

-Glossary Service Cost (Component of Net Periodic Pension Cost)

-URI http://asc.fasb.org/extlink&oid=6525008

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (a)(1)

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