Fair Value Measurements Fair Value Measurements, Schedule of Quantitative Information for Level 3 Derivative Contracts (Details)	9 Months Ended
	Sep. 30, 2015 USD ($)
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Midwest Premium Swap Asset Beginning Curve Value	$ 0.070
Midwest Premium Swap Asset Ending Curve Value	0.063
Midwest Premium Swap Liability Ending Curve Value	0.063
Midwest Premium Swap Liability Beginning Curve Value	$ 0.070