Long-Term Debt	3 Months Ended
Mar. 31, 2012
Long-Term Debt [Abstract]
Long-Term Debt	NOTE F. Long-term Debt The Company's long-term debt consists of senior notes and revolving credit facilities, including the effects of net deferred fair value hedge losses and issuance discounts and premiums. *Credit Facility.* During March 2011, the Company entered into a Second Amended and Restated 5-Year Revolving Credit Agreement (the "Credit Facility") with a syndicate of financial institutions that matures in March 2016, unless extended in accordance with the terms of the Credit Facility. As of March 31, 2012, the Company had $67.0 million of outstanding borrowings under the Credit Facility and $65.1 million of undrawn letters of credit, all of which were commitments under the Credit Facility, leaving the Company with $1.1 billion of unused borrowing capacity under the Credit Facility. *Pioneer Southwest Credit Facility.* During March 2012, Pioneer entered into an Amended and Restated 5-Year Revolving Credit Agreement (the "Pioneer Southwest Credit Facility") with a syndicate of financial institutions that matures in March 2017, unless extended in accordance with the terms of the Pioneer Southwest Credit Facility. The Pioneer Southwest Credit Facility replaced Pioneer Southwest's 5-Year Revolving Credit Agreement entered into in May 2008 and provides for aggregate loan commitments of $300 million. As of March 31, 2012, the Pioneer Southwest had $50.0 million of outstanding borrowings and $250.0 million of unused borrowing capacity under the Pioneer Southwest Credit Facility. The Pioneer Southwest Credit Facility is available for general partnership purposes, including working capital, capital expenditures and distributions. Borrowings under the Pioneer Southwest Credit Facility may be in the form of Eurodollar rate loans, base rate committed loans or swing line loans. The Pioneer Southwest Credit Facility contains certain financial covenants, including (i) the maintenance of a quarter end maximum leverage ratio of not more than 3.5 to 1.00 and (ii) the maintenance of a ratio of the net present value of Pioneer Southwest's projected future cash flows from its oil and gas properties to total debt of at least 1.75 to 1.0. Total borrowings may not exceed $300 million, subject to the Pioneer Southwest's right to increase the borrowing commitments by an additional maximum amount of $100 million if the lenders increase their commitments or if commitments of new lenders are added. As of March 31, 2012, the Company and Pioneer Southwest were in compliance with all of their debt covenants. *Convertible senior notes.* As of March 31, 2012 and December 31, 2011, the Company had $479.9 million of 2.875% Convertible Senior Notes outstanding. The 2.875% Convertible Senior Notes are convertible under certain circumstances, using a net share settlement process, into a combination of cash and the Company's common stock pursuant to a formula set forth in the indenture supplement pursuant to which the 2.875% Convertible Senior Notes were issued. The Company's stock prices during each of March 2012 and March 2011 met the average price threshold that causes the Company's 2.875% Convertible Senior Notes to become convertible at the option of the holders during the following three month period. Associated therewith, certain holders of the 2.875% Convertible Senior Notes tendered $70 thousand principal amount of the notes for conversion during the three months ended June 30, 2011. During July and August 2011, the Company paid the tendering holders a total of $71 thousand cash and issued to the tendering holders 340 shares of the Company's common stock in accordance with the terms of the 2.875% Convertible Senior Notes indenture supplement. Effective April 1, 2012, the Company's 2.875% Convertible Senior Notes are convertible at the option of the holders for the three months ended June 30, 2012 and may become convertible in future quarters depending on the Company's stock price or other conditions. If the 2.875% Convertible Senior Notes had qualified for and been converted as of March 31, 2012, the note holders would have received $479.9 million of cash and approximately 3.5 million shares of the Company's common stock, which was valued at $386.1 million at March 31, 2012. On January 15, 2013, the 2.875% Convertible Senior Notes become redeemable at the option of the Company and on January 15, 2013, January 15, 2018, January 15, 2023, January 15, 2028 and January 15, 2033 the holders my require the Company to repurchase the notes for cash. The Company has the intent and ability to fund cash payments that may be required upon the conversion, redemption or repurchase of the 2.875% Convertible Senior Notes with borrowing capacity under the Credit Facility. Accordingly, the 2.875% Convertible Senior Notes are classified as long-term debt in the accompanying balance sheets.

NOTE F. Long-term Debt

The Company's long-term debt consists of senior notes and revolving credit facilities, including the effects of net deferred fair value hedge losses and issuance discounts and premiums.

Credit Facility. During March 2011, the Company entered into a Second Amended and Restated 5-Year Revolving Credit Agreement (the "Credit Facility") with a syndicate of financial institutions that matures in March 2016, unless extended in accordance with the terms of the Credit Facility. As of March 31, 2012, the Company had $67.0 million of outstanding borrowings under the Credit Facility and $65.1 million of undrawn letters of credit, all of which were commitments under the Credit Facility, leaving the Company with $1.1 billion of unused borrowing capacity under the Credit Facility.

Pioneer Southwest Credit Facility. During March 2012, Pioneer entered into an Amended and Restated 5-Year Revolving Credit Agreement (the "Pioneer Southwest Credit Facility") with a syndicate of financial institutions that matures in March 2017, unless extended in accordance with the terms of the Pioneer Southwest Credit Facility. The Pioneer Southwest Credit Facility replaced Pioneer Southwest's 5-Year Revolving Credit Agreement entered into in May 2008 and provides for aggregate loan commitments of $300 million. As of March 31, 2012, the Pioneer Southwest had $50.0 million of outstanding borrowings and $250.0 million of unused borrowing capacity under the Pioneer Southwest Credit Facility.

The Pioneer Southwest Credit Facility is available for general partnership purposes, including working capital, capital expenditures and distributions. Borrowings under the Pioneer Southwest Credit Facility may be in the form of Eurodollar rate loans, base rate committed loans or swing line loans. The Pioneer Southwest Credit Facility contains certain financial covenants, including (i) the maintenance of a quarter end maximum leverage ratio of not more than 3.5 to 1.00 and (ii) the maintenance of a ratio of the net present value of Pioneer Southwest's projected future cash flows from its oil and gas properties to total debt of at least 1.75 to 1.0.

Total borrowings may not exceed $300 million, subject to the Pioneer Southwest's right to increase the borrowing commitments by an additional maximum amount of $100 million if the lenders increase their commitments or if commitments of new lenders are added.

As of March 31, 2012, the Company and Pioneer Southwest were in compliance with all of their debt covenants.

Convertible senior notes. As of March 31, 2012 and December 31, 2011, the Company had $479.9 million of 2.875% Convertible Senior Notes outstanding. The 2.875% Convertible Senior Notes are convertible under certain circumstances, using a net share settlement process, into a combination of cash and the Company's common stock pursuant to a formula set forth in the indenture supplement pursuant to which the 2.875% Convertible Senior Notes were issued.

The Company's stock prices during each of March 2012 and March 2011 met the average price threshold that causes the Company's 2.875% Convertible Senior Notes to become convertible at the option of the holders during the following three month period. Associated therewith, certain holders of the 2.875% Convertible Senior Notes tendered $70 thousand principal amount of the notes for conversion during the three months ended June 30, 2011. During July and August 2011, the Company paid the tendering holders a total of $71 thousand cash and issued to the tendering holders 340 shares of the Company's common stock in accordance with the terms of the 2.875% Convertible Senior Notes indenture supplement.

Effective April 1, 2012, the Company's 2.875% Convertible Senior Notes are convertible at the option of the holders for the three months ended June 30, 2012 and may become convertible in future quarters depending on the Company's stock price or other conditions. If the 2.875% Convertible Senior Notes had qualified for and been converted as of March 31, 2012, the note holders would have received $479.9 million of cash and approximately 3.5 million shares of the Company's common stock, which was valued at $386.1 million at March 31, 2012.

On January 15, 2013, the 2.875% Convertible Senior Notes become redeemable at the option of the Company and on January 15, 2013, January 15, 2018, January 15, 2023, January 15, 2028 and January 15, 2033 the holders my require the Company to repurchase the notes for cash. The Company has the intent and ability to fund cash payments that may be required upon the conversion, redemption or repurchase of the 2.875% Convertible Senior Notes with borrowing capacity under the Credit Facility. Accordingly, the 2.875% Convertible Senior Notes are classified as long-term debt in the accompanying balance sheets.