Impairment	12 Months Ended
Dec. 31, 2011
Impairment [Abstract]
Impairment	NOTE R. Impairment The Company reviews its long-lived assets for impairment, including oil and gas proved properties, whenever events or circumstances indicate that their carrying values may not be fully recoverable. During the years ended 2011 and 2009, the Company recognized $354.4 million and $21.1 million, respectively, of charges from impairment of oil and gas proved properties. *2011 impairment.* During the third and fourth quarters of 2011, events and circumstances provided indications of possible impairment of certain of the Company's dry gas assets, including oil and gas proved properties in the Company's Edwards, Austin Chalk, Raton and Barnett Shale fields. The events and circumstances indicating possible impairment of these fields were primarily related to a reduction in Management's Price Outlook for gas that led to a decrease in estimated future undiscounted net cash flows attributable to each fields' proved reserves. During the fourth quarter of 2011, the estimate of undiscounted future net cash flows attributable to the Company's Edwards and Austin Chalk fields in South Texas indicated that their carrying amounts were partially unrecoverable. Consequently, the Company recorded $354.4 million of noncash impairment charges to reduce the carrying values of these fields to their estimated fair values, represented by the estimated discounted future cash flows attributable to the assets, which were derived from Level 3 fair value inputs, including Management's Price Outlook and the primary factors described in Note B and below. *2009 impairment.* During the first quarter of 2009, declines in commodity prices provided indications that the carrying values of the Company's oil and gas properties in the Uinta/Piceance area may have been impaired. The Company's estimates of the undiscounted future cash flows attributed to the assets indicated that their carrying amounts were not expected to be recovered. Consequently, the Company recorded noncash charges during the first quarter of 2009 of $21.1 million to reduce the carrying value of the Uinta/Piceance area oil and gas properties. During 2010, the Company sold substantially all of its oil and gas properties in the Uinta/Piceance area. See Note M for more information on asset divestitures. The impairment charges reduced the oil and gas properties' carrying values to their estimated fair values on those dates, represented by the estimated discounted future cash flows attributable to the assets, which were derived from Level 3 fair value inputs. *Impairment risks.* The Company's estimates of undiscounted future net cash flows attributable to the Raton and Barnett Shale fields' oil and gas properties indicated on December 31, 2011 that their carrying amounts were expected to be recovered. However, the carrying values of these fields continue to be at risk for impairment if future estimates of undiscounted cash flows decline. As of December 31, 2011, the Company's Raton and Barnett Shale fields have carrying values of $2.3 billion and $456.8 million, respectively. It is reasonably possible that the estimate of undiscounted future net cash flows attributable to these or other properties may change in the future resulting in the need to impair their carrying values. The primary factors that may affect estimates of future cash flows are (i) future reserve adjustments, both positive and negative, to proved reserves and appropriate risk-adjusted probable and possible reserves, (ii) results of future drilling activities, (iii) Management's Price Outlooks and (iv) increases or decreases in production and capital costs associated with the fields.

NOTE R. Impairment

The Company reviews its long-lived assets for impairment, including oil and gas proved properties, whenever events or circumstances indicate that their carrying values may not be fully recoverable. During the years ended 2011 and 2009, the Company recognized $354.4 million and $21.1 million, respectively, of charges from impairment of oil and gas proved properties.

2011 impairment. During the third and fourth quarters of 2011, events and circumstances provided indications of possible impairment of certain of the Company's dry gas assets, including oil and gas proved properties in the Company's Edwards, Austin Chalk, Raton and Barnett Shale fields. The events and circumstances indicating possible impairment of these fields were primarily related to a reduction in Management's Price Outlook for gas that led to a decrease in estimated future undiscounted net cash flows attributable to each fields' proved reserves. During the fourth quarter of 2011, the estimate of undiscounted future net cash flows attributable to the Company's Edwards and Austin Chalk fields in South Texas indicated that their carrying amounts were partially unrecoverable. Consequently, the Company recorded $354.4 million of noncash impairment charges to reduce the carrying values of these fields to their estimated fair values, represented by the estimated discounted future cash flows attributable to the assets, which were derived from Level 3 fair value inputs, including Management's Price Outlook and the primary factors described in Note B and below.

2009 impairment. During the first quarter of 2009, declines in commodity prices provided indications that the carrying values of the Company's oil and gas properties in the Uinta/Piceance area may have been impaired. The Company's estimates of the undiscounted future cash flows attributed to the assets indicated that their carrying amounts were not expected to be recovered. Consequently, the Company recorded noncash charges during the first quarter of 2009 of $21.1 million to reduce the carrying value of the Uinta/Piceance area oil and gas properties. During 2010, the Company sold substantially all of its oil and gas properties in the Uinta/Piceance area. See Note M for more information on asset divestitures. The impairment charges reduced the oil and gas properties' carrying values to their estimated fair values on those dates, represented by the estimated discounted future cash flows attributable to the assets, which were derived from Level 3 fair value inputs.

Impairment risks. The Company's estimates of undiscounted future net cash flows attributable to the Raton and Barnett Shale fields' oil and gas properties indicated on December 31, 2011 that their carrying amounts were expected to be recovered. However, the carrying values of these fields continue to be at risk for impairment if future estimates of undiscounted cash flows decline. As of December 31, 2011, the Company's Raton and Barnett Shale fields have carrying values of $2.3 billion and $456.8 million, respectively.

It is reasonably possible that the estimate of undiscounted future net cash flows attributable to these or other properties may change in the future resulting in the need to impair their carrying values. The primary factors that may affect estimates of future cash flows are (i) future reserve adjustments, both positive and negative, to proved reserves and appropriate risk-adjusted probable and possible reserves, (ii) results of future drilling activities, (iii) Management's Price Outlooks and (iv) increases or decreases in production and capital costs associated with the fields.