Environmental Exit Costs, Gallons of Wastewater Transported

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Commitments and Contingencies (Additional Information) (Details) gal in Thousands, a in Thousands		12 Months Ended
	Nov. 04, 2015 USD ($) a	Dec. 31, 2008 gal	Dec. 31, 2015 USD ($) MMBoe
Unfavorable Regulatory Action
Site Contingency [Line Items]
Order for payment of additional royalties			$ 129,700
Preliminary estimates of order maximum liabilities for additional royalties			$ 24,000,000
Sylacauga, Talladega County, Alabama
Site Contingency [Line Items]
Gallons of wastewater transported \| gal		3
Crude Oil and Natural Gas
Site Contingency [Line Items]
Oil and gas delivery commitments, volume \| MMBoe			5.8
Pending Litigation \| Energen vs. Endeavor Energy Resources
Site Contingency [Line Items]
Number of acres with cloud on the title \| a	10
Amount of counterclaim	$ 300,000,000