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