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Commodity Derivative Instruments (Schedule of Fair Value of Derivatives) (Details) (Commodity Contract [Member], USD $)
In Thousands, unless otherwise specified
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Feb. 28, 2014
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Aug. 31, 2013
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Current Assets [Member]
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| Derivatives, Fair Value [Line Items] |
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| Derivative asset, Gross Amount Recognized |
$ 425 |
$ 28 |
| Derivative asset, Gross Amounts Offset in the Balance Sheet |
(425) |
(28) |
| Derivative asset, Net |
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Noncurrent Assets [Member]
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| Derivatives, Fair Value [Line Items] |
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| Derivative asset, Gross Amount Recognized |
348 |
182 |
| Derivative asset, Gross Amounts Offset in the Balance Sheet |
(348) |
(182) |
| Derivative asset, Net |
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Current Liabilities [Member]
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| Derivatives, Fair Value [Line Items] |
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| Derivative liability, Gross Amount Recognized |
2,100 |
2,343 |
| Derivative liability, Gross Amounts Offset in the Balance Sheet |
(425) |
(28) |
| Derivative liability, Net |
1,675 |
2,315 |
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Noncurrent Liabilities [Member]
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| Derivatives, Fair Value [Line Items] |
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| Derivative liability, Gross Amount Recognized |
491 |
516 |
| Derivative liability, Gross Amounts Offset in the Balance Sheet |
(348) |
(182) |
| Derivative liability, Net |
$ 143 |
$ 334 |