Fair Value Measurements Fair Value Measurements, Schedule of Quantitative Information for Level 3 Derivative Contracts (Details)	6 Months Ended
Jun. 30, 2015 USD ($)
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Midwest Premium Swap Beginning Curve Value	$ 0.082
Midwest Premium Swap Contracts Ending Curve Value	$ 0.070

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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