Impairment	12 Months Ended
Dec. 31, 2013
Impairment [Abstract]
Impairment	Impairment Property, Plant and Equipment As deemed necessary based on events in 2012 and 2013, the Company analyzed various property, plant and equipment for impairment. Estimated fair values of these assets were calculated using a discounted cash flow method or recent offers from third-party purchasers. Gas Treating Plants and Other Midstream Assets. In the fourth quarter of 2012, the Company substantially completed construction of the Century Plant, a CO₂ treatment plant in Pecos County, Texas (the “Century Plant”), and associated compression and pipeline facilities pursuant to an agreement with Occidental Petroleum Corporation (“Occidental”). In conjunction with the substantial completion and resulting diversion of the Company’s high CO₂ natural gas production from its legacy gas treating plants to the Century Plant, the Company evaluated its legacy gas treating plants and CO₂compression facilities for impairment. Due to prevailing low natural gas prices, the Company’s natural gas production was not projected to reach the available treating capacity at the Century Plant. As such, the Company determined the use of its legacy gas treating plants and CO₂ compression facilities in west Texas was limited, and accordingly, recorded a $79.3 million impairment of its gas treating plants and CO₂ compression facilities at December 31, 2012. During 2013, the Company evaluated certain midstream pipe inventory, natural gas compressors, gas treating plants and a CO₂ compressor station for impairment after determining that their future use was limited. As a result of these evaluations, the Company recorded impairments of $12.2 million during the year ended December 31, 2013 on these assets to reduce their carrying value to market value. Drilling Assets. As a result of the Company’s entry into an agreement to sell the Permian Properties, the Company performed an impairment assessment of its drilling rigs as of December 31, 2012 by calculating the estimated future cash flows to be generated by the rigs and their related assets. As the undiscounted future cash flows were in excess of the assets’ carrying value, no impairment was indicated at that time. During the second and third quarters of 2013, the Company committed to plans to sell various drilling assets. The net book value of these drilling assets was adjusted to fair value, resulting in an impairment of $11.1 million and a combined remaining net book value at that time of $6.2 million. Fair value for the drilling assets was estimated based on recent offers received from third parties with consideration of current market conditions. Including subsequent asset sales the remaining net book value of these assets was $5.9 million at December 31, 2013. These assets are included in other current assets in the accompanying consolidated balance sheet at December 31, 2013 as the Company intends to sell the assets within a year. Other Property, Plant and Equipment. In the second quarter of 2013, the Company committed to a plan to sell a corporate asset. The net book value of the corporate asset was adjusted to fair value, resulting in an impairment of $2.9 million during the year ended December 31, 2013. The fair value of the corporate asset was based on a current offer from a third-party purchaser, which is considered a Level 3 input. The corporate asset was sold in the fourth quarter of 2013. The Company recorded a $1.3 million impairment in 2012 due to the write-off of certain software costs as the software was determined to be obsolete. Goodwill In December 2012, the Company entered into an agreement to sell the Permian Properties, which the Company determined to be a triggering event for purposes of evaluating goodwill as the Permian Properties are included in the exploration and production segment, the reporting unit to which goodwill was assigned. As such, an impairment test was performed as of December 31, 2012. Primarily as a result of a decrease in the Company’s probable reserves as of December 31, 2012, which are one of the significant components in the determination of the fair value of the reporting unit, the carrying value of the reporting unit exceeded the fair value. Probable reserves used in the reporting unit fair value calculation decreased due to their reclassification to possible reserves as a result of the Company’s year-end evaluation of drilling results across its acreage in the Mississippian formation. Possible reserves are not included in the fair value calculation of the reporting unit. The Company performed step two of the impairment test, which indicated the entire balance of goodwill was impaired. As a result, the Company recorded an impairment equal to the carrying amount of goodwill, or $235.4 million, at December 31, 2012, which is included in impairment in the accompanying consolidated statement of operations for the year ended December 31, 2012.

Impairment

Property, Plant and Equipment

As deemed necessary based on events in 2012 and 2013, the Company analyzed various property, plant and equipment for impairment. Estimated fair values of these assets were calculated using a discounted cash flow method or recent offers from third-party purchasers.

Gas Treating Plants and Other Midstream Assets. In the fourth quarter of 2012, the Company substantially completed construction of the Century Plant, a CO₂ treatment plant in Pecos County, Texas (the “Century Plant”), and associated compression and pipeline facilities pursuant to an agreement with Occidental Petroleum Corporation (“Occidental”). In conjunction with the substantial completion and resulting diversion of the Company’s high CO₂ natural gas production from its legacy gas treating plants to the Century Plant, the Company evaluated its legacy gas treating plants and CO₂compression facilities for impairment. Due to prevailing low natural gas prices, the Company’s natural gas production was not projected to reach the available treating capacity at the Century Plant. As such, the Company determined the use of its legacy gas treating plants and CO₂ compression facilities in west Texas was limited, and accordingly, recorded a $79.3 million impairment of its gas treating plants and CO₂ compression facilities at December 31, 2012.

During 2013, the Company evaluated certain midstream pipe inventory, natural gas compressors, gas treating plants and a CO₂ compressor station for impairment after determining that their future use was limited. As a result of these evaluations, the Company recorded impairments of $12.2 million during the year ended December 31, 2013 on these assets to reduce their carrying value to market value.

Drilling Assets. As a result of the Company’s entry into an agreement to sell the Permian Properties, the Company performed an impairment assessment of its drilling rigs as of December 31, 2012 by calculating the estimated future cash flows to be generated by the rigs and their related assets. As the undiscounted future cash flows were in excess of the assets’ carrying value, no impairment was indicated at that time.

During the second and third quarters of 2013, the Company committed to plans to sell various drilling assets. The net book value of these drilling assets was adjusted to fair value, resulting in an impairment of $11.1 million and a combined remaining net book value at that time of $6.2 million. Fair value for the drilling assets was estimated based on recent offers received from third parties with consideration of current market conditions. Including subsequent asset sales the remaining net book value of these assets was $5.9 million at December 31, 2013. These assets are included in other current assets in the accompanying consolidated balance sheet at December 31, 2013 as the Company intends to sell the assets within a year.

Other Property, Plant and Equipment. In the second quarter of 2013, the Company committed to a plan to sell a corporate asset. The net book value of the corporate asset was adjusted to fair value, resulting in an impairment of $2.9 million during the year ended December 31, 2013. The fair value of the corporate asset was based on a current offer from a third-party purchaser, which is considered a Level 3 input. The corporate asset was sold in the fourth quarter of 2013.

The Company recorded a $1.3 million impairment in 2012 due to the write-off of certain software costs as the software was determined to be obsolete.

Goodwill

In December 2012, the Company entered into an agreement to sell the Permian Properties, which the Company determined to be a triggering event for purposes of evaluating goodwill as the Permian Properties are included in the exploration and production segment, the reporting unit to which goodwill was assigned. As such, an impairment test was performed as of December 31, 2012. Primarily as a result of a decrease in the Company’s probable reserves as of December 31, 2012, which are one of the significant components in the determination of the fair value of the reporting unit, the carrying value of the reporting unit exceeded the fair value. Probable reserves used in the reporting unit fair value calculation decreased due to their reclassification to possible reserves as a result of the Company’s year-end evaluation of drilling results across its acreage in the Mississippian formation. Possible reserves are not included in the fair value calculation of the reporting unit. The Company performed step two of the impairment test, which indicated the entire balance of goodwill was impaired. As a result, the Company recorded an impairment equal to the carrying amount of goodwill, or $235.4 million, at December 31, 2012, which is included in impairment in the accompanying consolidated statement of operations for the year ended December 31, 2012.