Discontinued Operations (Results of Operations of Hankinson) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Income (loss) from discontinued operations	$ 38,749	$ 20,903	$ 80,898
Discontinued Operations, Disposed of by Sale [Member] \| Hankinson Renewable Energy, LLC [Member]
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Revenues		0	366,707
Income (loss) from operations before income taxes		0	40,130
Gain on sale before income taxes		1,202	80,834
Total income (loss) from discontinued operations before taxes		1,202	120,964
Provision for income taxes		421	42,257
Income (loss) from discontinued operations		$ 781	$ 78,707

Amount before tax of income (loss) from a discontinued operation. Includes, but is not limited to, the income (loss) from operations during the phase-out period, gain (loss) on disposal, gain (loss) for reversal of write-down (write-down) to fair value, less cost to sell, and adjustments to a prior period gain (loss) on disposal.

Amount of tax expense (benefit) related to a discontinued operation. Includes, but is not limited to, tax expense (benefit) related to income (loss) from operations during the phase-out period, tax expense (benefit) related to gain (loss) on disposal, tax expense (benefit) related to gain (loss) for reversal of write-down (write-down) to fair value, less cost to sell, and tax expense (benefit) related to adjustments of a prior period gain (loss) on disposal.

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- Definition

Amount after tax of income (loss) from a discontinued operation including the portion attributable to the noncontrolling interest. Includes, but is not limited to, the income (loss) from operations during the phase-out period, gain (loss) on disposal, gain (loss) for reversal of write-down (write-down) to fair value, less cost to sell, and adjustments to a prior period gain (loss) on disposal.

+ References

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Reference 10: http://www.xbrl.org/2003/role/presentationRef
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