Assets Held for Sale Assets Held for Sale	9 Months Ended
Sep. 30, 2013
Assets held for sale [Abstract]
Divestitures and Assets Held-for-sale	Note 3 – Assets Held for Sale Assets are classified as held for sale when the Company commits to a plan to sell the assets and there is reasonable certainty the sale will take place within one year. Upon classification as held for sale, long-lived assets are no longer depreciated or depleted, and a measurement for impairment is performed to identify and expense any excess of carrying value over fair value less estimated costs to sell. Subsequent changes to the estimated fair value less the costs to sell will impact the measurement of assets held for sale for which fair value less estimated costs to sell is determined to be less than the carrying value of the assets. As of September 30, 2013, the accompanying condensed consolidated balance sheets (“accompanying balance sheets”) present $400.4 million of assets held for sale, net of accumulated depletion, depreciation, and amortization expense. A corresponding asset retirement obligation liability of $25.3 million is separately presented. The assets held for sale include certain assets located in all four of the Company’s regions, all of which are recorded at the lesser of their carrying values or their respective fair value less estimated costs to sell. Write-downs to fair value less estimated costs to sell of $8.7 million for the three months ended September 30, 2013, and $10.1 million for the nine months ended September 30, 2013, are reflected in the loss on divestiture activity line item in the accompanying condensed consolidated statements of operations (“accompanying statements of operations”). The Company entered into multiple agreements to divest certain assets located in its Mid-Continent and Rocky Mountain regions that were classified as held for sale at September 30, 2013. The closings of these transactions are subject to the satisfaction of certain closing conditions, including the resolution of any title and environmental defects exceeding specified levels. Sales prices less estimated costs to sell were in excess of the carrying values of these assets as of September 30, 2013. The Company determined that these planned asset sales do not qualify for discontinued operations accounting under financial statement presentation authoritative guidance.

Note 3 – Assets Held for Sale

Assets are classified as held for sale when the Company commits to a plan to sell the assets and there is reasonable certainty the sale will take place within one year. Upon classification as held for sale, long-lived assets are no longer depreciated or depleted, and a measurement for impairment is performed to identify and expense any excess of carrying value over fair value less estimated costs to sell. Subsequent changes to the estimated fair value less the costs to sell will impact the measurement of assets held for sale for which fair value less estimated costs to sell is determined to be less than the carrying value of the assets.

As of September 30, 2013, the accompanying condensed consolidated balance sheets (“accompanying balance sheets”) present $400.4 million of assets held for sale, net of accumulated depletion, depreciation, and amortization expense. A corresponding asset retirement obligation liability of $25.3 million is separately presented. The assets held for sale include certain assets located in all four of the Company’s regions, all of which are recorded at the lesser of their carrying values or their respective fair value less estimated costs to sell. Write-downs to fair value less estimated costs to sell of $8.7 million for the three months ended September 30, 2013, and $10.1 million for the nine months ended September 30, 2013, are reflected in the loss on divestiture activity line item in the accompanying condensed consolidated statements of operations (“accompanying statements of operations”).

The Company entered into multiple agreements to divest certain assets located in its Mid-Continent and Rocky Mountain regions that were classified as held for sale at September 30, 2013. The closings of these transactions are subject to the satisfaction of certain closing conditions, including the resolution of any title and environmental defects exceeding specified levels. Sales prices less estimated costs to sell were in excess of the carrying values of these assets as of September 30, 2013.

The Company determined that these planned asset sales do not qualify for discontinued operations accounting under financial statement presentation authoritative guidance.