Organization and Basis of Presentation - Derivative Gains and Losses (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative instruments, net	$ (84,846)	$ 55,244	$ (138,237)	$ 36,288
Commodity contracts
Derivative Instruments, Gain (Loss) [Line Items]
Open non-cash mark-to-market gains (losses) on derivative instruments	(59,621)	56,149	(93,302)	15,101
Closed gains (losses) on derivative instruments	(25,225)	(905)	(44,935)	21,187
Gain (loss) on derivative instruments, net	$ (84,846)	$ 55,244	$ (138,237)	$ 36,288

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4A

-Subparagraph (b)

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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- Definition

Aggregate net gain (loss) on all derivative instruments recognized in earnings during the period, before tax effects.

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- Definition

The difference between the book value and the sale price of options, swaps, futures, forward contracts, and other derivative instruments. This element refers to the gain (loss) included in earnings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 10

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

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