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Subsequent Events (Details) (USD $) | 1 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Feb. 29, 2012 | Jan. 31, 2012 Long Term Commitments [Member] | Dec. 31, 2011 Long Term Commitments [Member] | Jan. 31, 2012 Millions Of Barrels [Member] Long Term Commitments [Member]
Subsequent Event [Line Items] |  |  |  |
Minimum quantity of delivery |  |  |  | 4.4
Future obligations under supply agreements |  | $ 13,000,000 | $ 54,500,000 |
Number of barrels converted for deferred premium put contracts | 1,000 |  |  |
Selling price of costless collar in call option | $ 111.30 |  |  |

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