Derivative Instruments and Hedging Activities - Narrative (Details) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2014	Sep. 30, 2015	Dec. 31, 2014	Apr. 01, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Accumulated other comprehensive income (loss)			$ (2,151,000)	$ (2,151,000)
Unrealized losses included in accumulated other comprehensive income and reclassified into natural gas and crude oil revenues, net of tax			$ 0	$ 0
Ineffectiveness related to derivative instruments	$ 0	$ 0
Commodity contracts | Gain (loss) on cash flow hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Unrealized losses included in accumulated other comprehensive income and reclassified into natural gas and crude oil revenues, pre-tax					$ 73,400,000
Accumulated other comprehensive income (loss)					$ (44,200,000)