Benefit Plan Assumptions (Detail)	12 Months Ended
Aug. 31, 2012	Aug. 31, 2011	Aug. 31, 2010
Weighted-average assumptions used to calculate net periodic expense:
Expected return on plan assets	0.07%
Pension Benefits [Member]
Weighted-average assumptions used to calculate net periodic expense:
Discount rate	5.87%	5.64%	5.98%
Expected return on plan assets	8.00%	8.00%	8.00%
Rate of compensation increase	3.00%	4.00%	4.00%
Weighted-average assumptions used to calculate benefit obligations at August 31:
Discount rate	4.28%	5.87%	5.64%
Expected return on plan assets	7.00%	8.00%	8.00%
Rate of compensation increase	3.00%	3.00%	4.00%
Other Benefits [Member]
Weighted-average assumptions used to calculate net periodic expense:
Discount rate	5.87%	5.64%	5.98%
Weighted-average assumptions used to calculate benefit obligations at August 31:
Discount rate	4.28%	5.87%	5.64%

Defined Benefit Plan Assumptions Used Calculating Benefit Obligation Expected Long Term Return On Assets

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- Definition

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

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph j

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (k)(1)

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- Definition

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

+ References

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

+ References

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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 20

-Section 50

-Paragraph 1

-Subparagraph (k)(3)

-URI http://asc.fasb.org/extlink&oid=21915506&loc=d3e1928-114920

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 87

-Paragraph 264

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph j

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: 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

-URI http://asc.fasb.org/extlink&oid=6512013

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- Definition

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

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