Impairment	12 Months Ended
Dec. 31, 2014
Asset Impairment Charges [Abstract]
Impairment	Impairment Property, Plant and Equipment As deemed necessary based on events in 2014, 2013 and 2012, the Company analyzed various property, plant and equipment for impairment. Estimated fair values of these assets were determined using a combination of the discounted cash flow method, recent offers from third-party purchasers or prices of comparable assets with consideration of current market conditions. Given the significance of the unobservable nature of a number of the inputs, these are considered Level 3 on the fair value hierarchy discussed in Note 5. Oil and Natural Gas Properties. The Company incurred an impairment of $164.8 million for the year ended December 31, 2014 due to a full cost ceiling limitation resulting from the divestiture of the Gulf Properties, as the present value of future net revenues associated with the Gulf Properties exceeded the associated reduction to the full cost pool. Drilling Assets. As a result of the Company’s fulfillment of its drilling obligation with the Permian Trust and the downward trend in oil prices that began in the second half of 2014, demand for the Company’s drilling and oilfield services in the Permian region declined significantly. At December 31, 2014, the Company determined the future use of its drilling and oilfield services assets in this region was limited and recorded an impairment of $24.3 million on these assets. During 2014 and 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 impairments of $3.1 million and $11.1 million for the years ended December 31, 2014 and 2013, respectively. The remaining net book value of these assets is included in other current assets in the accompanying consolidated balance sheet at December 31, 2014 as the Company intends to sell the assets within a year. 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. Gas Treating Plants and Other Midstream Assets. During 2014 and 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 $0.6 million and $12.2 million during the years ended December 31, 2014 and 2013, respectively, on these assets to reduce their carrying value to market value. In the fourth quarter of 2012, the Company substantially completed construction of the Century Plant, a CO₂ treatment plant in Pecos County, Texas, and associated compression and pipeline facilities pursuant to the agreement with 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. 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 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 2014, 2013 and 2012, the Company analyzed various property, plant and equipment for impairment. Estimated fair values of these assets were determined using a combination of the discounted cash flow method, recent offers from third-party purchasers or prices of comparable assets with consideration of current market conditions. Given the significance of the unobservable nature of a number of the inputs, these are considered Level 3 on the fair value hierarchy discussed in Note 5.

Oil and Natural Gas Properties. The Company incurred an impairment of $164.8 million for the year ended December 31, 2014 due to a full cost ceiling limitation resulting from the divestiture of the Gulf Properties, as the present value of future net revenues associated with the Gulf Properties exceeded the associated reduction to the full cost pool.

Drilling Assets. As a result of the Company’s fulfillment of its drilling obligation with the Permian Trust and the downward trend in oil prices that began in the second half of 2014, demand for the Company’s drilling and oilfield services in the Permian region declined significantly. At December 31, 2014, the Company determined the future use of its drilling and oilfield services assets in this region was limited and recorded an impairment of $24.3 million on these assets.

During 2014 and 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 impairments of $3.1 million and $11.1 million for the years ended December 31, 2014 and 2013, respectively. The remaining net book value of these assets is included in other current assets in the accompanying consolidated balance sheet at December 31, 2014 as the Company intends to sell the assets within a year.

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.

Gas Treating Plants and Other Midstream Assets. During 2014 and 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 $0.6 million and $12.2 million during the years ended December 31, 2014 and 2013, respectively, on these assets to reduce their carrying value to market value.

In the fourth quarter of 2012, the Company substantially completed construction of the Century Plant, a CO₂ treatment plant in Pecos County, Texas, and associated compression and pipeline facilities pursuant to the agreement with 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.

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 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.