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Derivatives (Narrative) (Details) (USD $) | 12 Months Ended | 0 Months Ended | 7 Months Ended | 12 Months Ended | 17 Months Ended | 0 Months Ended | 17 Months Ended
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Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2010 | Jul. 28, 2009 Costless Collar [Member] | Jul. 31, 2011 Costless Collar [Member] | Dec. 31, 2012 Costless Collar [Member] | Dec. 31, 2011 Costless Collar [Member] | Dec. 31, 2010 Costless Collar [Member] | Jun. 27, 2011 Cargill Agreement [Member] | Dec. 31, 2012 Cargill Agreement [Member]
Derivative [Line Items] |  |  |  |  |  |  |  |  |  |
Price agreement term |  |  |  | two |  |  |  |  | If the average price falls below $65 per barrel, then Cargill will pay to the Company the difference between $65 and the lower average price for 10,000 barrels per month in each month during when such lower average prices occur. |
Floor price (per barrel) |  |  |  | 60.00 |  |  |  |  | 65 |
Cap price (per barrel) |  |  |  | 81.50 |  |  |  |  |  |
Monthly volume (in barrels) |  |  |  |  | 7,375 |  |  | 9,500 |  | 10,000
Difference per barrel of Kansas Common plus bonus and current WTI NYMEX |  |  |  |  |  | 7 |  |  |  |
Contract description |  |  |  | two |  |  |  |  | If the average price falls below $65 per barrel, then Cargill will pay to the Company the difference between $65 and the lower average price for 10,000 barrels per month in each month during when such lower average prices occur. |
Derivative issuance cost per barrel |  |  |  |  |  |  |  |  | 2.20 |
Payments of derivative issuance costs |  |  |  |  |  |  |  |  | $ 374,000 |
Unrealized gain (loss) on derivatives | 140,000 | 450,000 | 630,000 |  |  |  |  |  |  |
Settlement payments |  |  | $ 130,000 |  |  |  | $ 860,000 |  |  |

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- Definition Difference per barrel of Kansas Common plus bonus and current WTI NYMEX. + References No definition available. + Details
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- Definition Settlement payments derivative contract + References No definition available. + Details
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- Definition The cap rate on a price risk derivative such as a cap or collar. A payment or receipt is triggered if the market rate exceeds the cap rate on the contract. + References No definition available. + Details
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- Definition Description of the relevant terms of the derivative. Includes the type of instrument, risk being hedged, notional amount, counterparty, inception date, maturity date, relevant interest rates, strike price, cap price, and floor price. + References No definition available. + Details
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- Definition Floor rate on a price risk derivative such as a floor or a collar. A payment or receipt is triggered if the market rate falls below the floor rate on the contract. + References No definition available. + Details
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- Definition The cash outflow for cost incurred directly with the issuance of a derivative security. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 18, 19, 20 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3291-108585 + Details
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- Definition The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of open derivatives, commodity, or energy contracts, held at each balance sheet date, that was included in earnings for the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 28 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585 + Details
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