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Fair Value Measurements and Derivative Instruments - Reconciliation of Gross Fair Value of Assets and Liabilities Subject to Offsetting Arrangements (Detail) (USD $)
In Thousands, unless otherwise specified |
May 31, 2014
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Aug. 31, 2013
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| Derivative Instruments and Hedging Activities Disclosures [Line Items] | ||
| Gross Amounts of Recognized Assets | $ 303 | $ 997 |
| Gross Liabilities Offset in the Balance Sheets | (3,202) | (485) |
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Commodity Contract [Member]
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| Derivative Instruments and Hedging Activities Disclosures [Line Items] | ||
| Gross Amounts of Recognized Assets | 303 | 997 |
| Gross Liabilities Offset in the Balance Sheets | (3,202) | (485) |
| Net Amount of Assets (Liabilities) | (2,899) | 512 |
| Cash Collateral on Deposit with Counterparty | 5,343 | 1,700 |
| Net Fair Value as Recorded in Balance Sheets | $ 2,444 | $ 2,212 |