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Commitment and contingencies variable interest entities (Details 4) (USD $) | Sep. 30, 2014 | Dec. 31, 2013 | Sep. 30, 2013
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Dakota Prairie Refining, LLC [Member] |  |  |
Variable Interest Entities [Line Items] |  |  |
Percent of ownership | 50.00% |  |
Total project costs | $ 300,000,000 |  |
Portion of capital commitment | 150,000,000 |  |
Partner portion of capital commitment | 75,000,000 |  |
Excess capital commitments | 300,000,000 |  |
Project cost estimate | 360,000,000 |  |
Term loan for project debt financing | 75,000,000 |  |
Dakota Prairie Refining, LLC [Member] | Cash and cash equivalents [Member] |  |  |
Variable Interest Entities [Line Items] |  |  |
Limited liability entity, consolidated, carrying amount, assets | 16,723,000 | 4,774,000 | 23,146,000
Dakota Prairie Refining, LLC [Member] | Accounts receivable [Member] |  |  |
Variable Interest Entities [Line Items] |  |  |
Limited liability entity, consolidated, carrying amount, assets | 150,000 | 0 | 1,000
Dakota Prairie Refining, LLC [Member] | Other current assets [Member] |  |  |
Variable Interest Entities [Line Items] |  |  |
Limited liability entity, consolidated, carrying amount, assets | 4,187,000 | 26,000 | 25,000
Dakota Prairie Refining, LLC [Member] | Total current assets [Member] |  |  |
Variable Interest Entities [Line Items] |  |  |
Limited liability entity, consolidated, carrying amount, assets | 21,060,000 | 4,800,000 | 23,172,000
Dakota Prairie Refining, LLC [Member] | Net property, plant and equipment [Member] |  |  |
Variable Interest Entities [Line Items] |  |  |
Limited liability entity, consolidated, carrying amount, assets | 314,551,000 | 172,073,000 | 123,297,000
Dakota Prairie Refining, LLC [Member] | Total assets [Member] |  |  |
Variable Interest Entities [Line Items] |  |  |
Limited liability entity, consolidated, carrying amount, assets | 335,611,000 | 176,873,000 | 146,469,000
Dakota Prairie Refining, LLC [Member] | Long-term debt due within one year [Member] |  |  |
Variable Interest Entities [Line Items] |  |  |
Limited liability entity, consolidated, carrying amount, liabilities | 3,000,000 | 3,000,000 | 3,000,000
Dakota Prairie Refining, LLC [Member] | Accounts payable [Member] |  |  |
Variable Interest Entities [Line Items] |  |  |
Limited liability entity, consolidated, carrying amount, liabilities | 36,541,000 | 8,904,000 | 20,313,000
Dakota Prairie Refining, LLC [Member] | Taxes payable [Member] |  |  |
Variable Interest Entities [Line Items] |  |  |
Limited liability entity, consolidated, carrying amount, liabilities | 323,000 | 5,000 | 0
Dakota Prairie Refining, LLC [Member] | Accrued compensation [Member] |  |  |
Variable Interest Entities [Line Items] |  |  |
Limited liability entity, consolidated, carrying amount, liabilities | 617,000 | 26,000 | 0
Dakota Prairie Refining, LLC [Member] | Other accrued liabilities [Member] |  |  |
Variable Interest Entities [Line Items] |  |  |
Limited liability entity, consolidated, carrying amount, liabilities | 633,000 | 461,000 | 363,000
Dakota Prairie Refining, LLC [Member] | Total current liabilities [Member] |  |  |
Variable Interest Entities [Line Items] |  |  |
Limited liability entity, consolidated, carrying amount, liabilities | 41,114,000 | 12,396,000 | 23,676,000
Dakota Prairie Refining, LLC [Member] | Long-term debt [Member] |  |  |
Variable Interest Entities [Line Items] |  |  |
Limited liability entity, consolidated, carrying amount, liabilities | 69,000,000 | 72,000,000 | 72,000,000
Dakota Prairie Refining, LLC [Member] | Total liabilities [Member] |  |  |
Variable Interest Entities [Line Items] |  |  |
Limited liability entity, consolidated, carrying amount, liabilities | 110,114,000 | 84,396,000 | 95,676,000
Fuel contract [Member] |  |  |
Variable Interest Entities [Line Items] |  |  |
Variable interest entity, reporting entity involvement, maximum loss exposure, amount | $ 12,000,000 |  |

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- Definition Excess capital commitments above this amount will be shared equally. + References No definition available. + Details
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