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Fair Value Measurements and Derivative Instruments - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified |
Nov. 30, 2012
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|---|---|
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Iowa Department of Economic Development Loans [Member]
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| Fair Value, Option, Quantitative Disclosures [Line Items] | |
| Carrying value of debt | $ 1.4 |
| Fair value of debt | 1.2 |
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Commodity Contract [Member]
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| Fair Value, Option, Quantitative Disclosures [Line Items] | |
| Deferred loss, net of tax, recorded in other comprehensive income | $ 0.2 |
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Commodity Contract [Member] | Designated as Hedging Instrument [Member] | Corn Futures [Member]
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| Fair Value, Option, Quantitative Disclosures [Line Items] | |
| Purchased corn positions | 6,300,000 |
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Commodity Contract [Member] | Firm Priced Starch and Ethanol Futures [Member] | Designated as Hedging Instrument [Member] | Corn Futures [Member]
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|
| Fair Value, Option, Quantitative Disclosures [Line Items] | |
| Purchased corn positions | 3,700,000 |
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Commodity Contract [Member] | Open Position [Member] | Designated as Hedging Instrument [Member] | Corn Futures [Member]
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|
| Fair Value, Option, Quantitative Disclosures [Line Items] | |
| Purchased corn positions | 2,600,000 |