Summary Of Significant Accounting Policies (Policy)

12 Months Ended

Dec. 31, 2011

Summary Of Significant Accounting Policies [Abstract]

Principles Of Consolidation

Principles of consolidation.The consolidated financial statements include the accounts of the Company and its wholly-owned and majority-owned subsidiaries since their acquisition or formation. In accordance with generally accepted accounting principles in the United States ("GAAP"), the Company proportionately consolidates certain affiliate partnerships that are less than wholly-owned and are involved in oil and gas producing activities. All material intercompany balances and transactions have been eliminated.

Certain reclassifications have been made to the 2010 and 2009 financial statement and footnote amounts in order to conform to the 2011 presentations.

Discontinued Operations

Discontinued operations.During December 2011, the Company committed to a plan to sell all of the assets and liabilities of its South Africa operations ("Pioneer South Africa"). The plan is expected to result in the sale of Pioneer South Africa during 2012. In accordance with GAAP, the Company has classified the Pioneer South Africa assets and liabilities as discontinued operations held for sale in the Company's accompanying consolidated balance sheet as of December 31, 2011, and Pioneer South Africa's results of operations as income from discontinued operations, net of tax in the accompanying consolidated statements of operations.

During December 2010, the Company committed to a plan to divest the capital stock of the Company's Tunisian subsidiaries ("Pioneer Tunisia"), which owned all of the Company's oil and gas properties in Tunisia. The Company completed the sale of Pioneer Tunisia during February 2011. Accordingly, the Company classified the assets and liabilities of Pioneer Tunisia as discontinued operations held for sale in the accompanying consolidated balance sheet as of December 31, 2010. The results of operations of Pioneer Tunisia are reported as income from discontinued operations, net of tax in the accompanying consolidated statements of operations.

During 2009, the Company sold its oil and gas properties in Mississippi and substantially all of its shelf properties in the Gulf of Mexico. The Company classified the results of operations attributable to these divestitures as discontinued operations, net of tax in the accompanying consolidated statement of operations.

Use Of Estimates In The Preparation Of Financial Statements

Use of estimates in the preparation of financial statements. Preparation of the accompanying consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting periods. Depletion of oil and gas properties and impairment of goodwill and proved and unproved oil and gas properties, in part, is determined using estimates of proved, probable and possible oil and gas reserves. There are numerous uncertainties inherent in the estimation of quantities of proved, probable and possible reserves and in the projection of future rates of production and the timing of development expenditures. Similarly, evaluations for impairment of proved and unproved oil and gas properties are subject to numerous uncertainties including, among others, estimates of future recoverable reserves; commodity price outlooks; foreign laws, restrictions and currency exchange rates; and export and excise taxes. Actual results could differ from the estimates and assumptions utilized.

Cash Equivalents

Cash equivalents.The Company's cash equivalents include depository accounts held by banks and marketable securities with original issuance maturities of 90 days or less.

Accounts Receivable

Accounts receivable.As of December 31, 2011 and 2010, the Company had accounts receivable – trade, net of allowances for bad debts, of $276.0 million and $237.5 million, respectively. The Company's accounts receivable – trade are primarily comprised of oil and gas sales receivable, joint interest receivables and other receivables for which the Company does not require collateral security.

As of December 31, 2011 and 2010, the Company's allowances for doubtful accounts totaled $1.1 million and $3.7 million, respectively. The Company establishes allowances for bad debts equal to the estimable portions of accounts and notes receivables for which failure to collect is considered probable. The Company estimates the portions of joint interest receivables for which failure to collect is probable based on percentages of joint interest receivables that are past due. The Company estimates the portions of other receivables for which failure to collect is probable based on the relevant facts and circumstances surrounding the receivable. Allowances for doubtful accounts are recorded as reductions to the carrying values of the receivables included in the Company's consolidated balance sheets and as charges to other expense in the consolidated statements of operations in the accounting periods during which failure to collect an estimable portion is determined to be probable.

	Year Ended December 31,
	2011			2010
	(in thousands)
Beginning allowance for doubtful accounts balance	$	3,674		$	14,299
Amount credited to costs and expenses, net		(1,693	)		(442	)
Other net decreases		(835	)		(10,183	)
Ending allowance for doubtful accounts balance	$	1,146		$	3,674

Investments

Investments.Investments in unaffiliated equity securities that have a readily determinable fair value are classified as "trading securities" if management's current intent is to hold them for the near term; otherwise, they are accounted for as "available-for-sale" securities. The Company reevaluates the classification of investments in unaffiliated equity securities at each balance sheet date. The carrying value of trading securities and available-for-sale securities are adjusted to fair value as of each balance sheet date and are included in other noncurrent assets in the accompanying balance sheets.

Unrealized holding gains are recognized for trading securities in interest and other income, and unrealized holding losses are recognized in other expense during the periods in which changes in fair value occur.

Unrealized holding gains and losses are recognized for available-for-sale securities as credits or charges to stockholders' equity and other comprehensive income (loss) during the periods in which changes in fair value occur. Realized gains and losses on the divestiture of available-for-sale securities are determined using the average cost method. The Company had no investments in available-for-sale securities as of December 31, 2011 or 2010.

Investments in unaffiliated equity securities that do not have a readily determinable fair value are measured at the lower of their original cost or the net realizable value of the investment. The Company had no significant equity security investments that did not have a readily determinable fair value as of December 31, 2011 or 2010.

Noncontrolling Interest In Consolidated Subsidiaries

Noncontrolling interest in consolidated subsidiaries.At December 31, 2011, the Company owns a 0.1 percent general partner interest and a 52.4 percent limited partner interest in Pioneer Southwest Energy Partners L.P. ("Pioneer Southwest"). Pioneer Southwest owns interests in certain oil and gas properties previously owned by the Company in the Spraberry field in the Permian Basin of West Texas. The financial position, results of operations, and cash flows of Pioneer Southwest are consolidated with those of the Company. On December 12, 2011, Pioneer Southwest completed the public offering of 4.4 million common units of Pioneer Southwest, representing limited partnership interests, at a per-unit offering price to the public of $29.20. Of the 4.4 million common units, Pioneer sold 1.8 million of its Pioneer Southwest common unit holdings and Pioneer Southwest issued 2.6 million new common units. The common unit sale resulted in the Company's limited ownership interest in Pioneer Southwest decreasing from 61.9 percent to 52.4 percent.

In accordance with GAAP, the Company records transfers of any gains or losses, net of taxes, from noncontrolling interests in consolidated subsidiaries to additional paid in capital proportionate to the ownership after giving effect to the sale of common units.

The following table presents the Company's net income (loss) attributable to common stockholders adjusted for transfers from noncontrolling interest in consolidated subsidiaries to additional paid in capital attributable to Pioneer Southwest's common unit offerings during the years ended December 31, 2011 and 2009:

	Year Ended December 31,
	2011		2010		2009
	(in thousands)
Net income (loss) attributable to common stockholders	$	834,489	$	605,208	$	(52,106	)
Transfers from the noncontrolling interest in consolidated subsidiaries:
Increase in additional paid in capital for Pioneer Southwest offering of 3.1 million common units issued on November 16, 2009		—		—		33,388
Increase in additional paid in capital for the sale of 1.8 million Pioneer Southwest common units on December 12, 2011, net of tax of $15.4 million		26,915		—		—
Increase in additional paid in capital for Pioneer Southwest offering of 2.6 million common units issued on December 12, 2011, net of tax of $23.7 million		8,104		—		—
Net transfers from noncontrolling interest		35,019		—		33,388
Net income (loss) attributable to common stockholders and transfers from noncontrolling interest	$	869,508	$	605,208	$	(18,718	)

During January 2010, Pioneer Natural Resources USA, Inc. ("PNR USA," a wholly-owned subsidiary of the Company) formed Sendero Drilling Company, LLC ("Sendero"). Sendero was formed to own and operate land-based drilling rigs in the United States. As of December 31, 2011, Sendero owned 15 drilling rigs operating under contract to PNR USA in the Spraberry field. PNR USA is the majority owner of Sendero.

The Company also owns the majority interests in certain other subsidiaries with operations in the United States. Noncontrolling interests in the net assets of consolidated subsidiaries totaled $162.3 million and $105.4 million as of December 31, 2011 and 2010, respectively. The Company recorded net income attributable to the noncontrolling interests of $47.4 million, $40.8 million and $9.8 million for the years ended December 31, 2011, 2010 and 2009 (principally related to Pioneer Southwest), respectively.

Investment In Unconsolidated Affiliate

Investment in unconsolidated affiliate.During 2010, the Company formed EFS Midstream LLC ("EFS Midstream") to own and operate gas and liquids gathering, treating and transportation assets in the Eagle Ford Shale area of South Texas. During June 2010, the Company sold a 49.9 percent member interest in EFS Midstream to an unaffiliated third party for $46.4 million of cash proceeds. Associated therewith, the Company recorded a $46.2 million deferred gain that is being amortized as a reduction in production costs over a 20 year period, representing the term of a continuing commitment of Pioneer to deliver production volumes through EFS Midstream handling and gathering facilities. The deferred gain is included in other current and noncurrent liabilities in the Company's accompanying consolidated balance sheet.

The Company does not have voting control of EFS Midstream. Consequently, the Company accounts for this investment under the equity method of accounting for investments in unconsolidated affiliates. Under the equity method, the Company's investment in unconsolidated affiliates is increased for investments made and the investor's share of the investee's net income, and decreased for distributions received, the carrying value of member interests sold and the investor's share of the investee's net losses. The Company's equity interest in the net income or loss of EFS Midstream is recorded in interest and other income in the Company's accompanying consolidated statement of operations.

See Note L for a detail of the Company's equity interest in the net income (loss) of EFS Midstream for the years ended December 31, 2011 and 2010.

Inventories

Inventories.Inventories were comprised of $297.9 million and $183.4 million of materials and supplies and $4.5 million and $3.9 million of commodities as of December 31, 2011 and 2010, respectively. The Company's materials and supplies inventory is primarily comprised of oil and gas drilling or repair items such as tubing, casing, chemicals, operating supplies and ordinary maintenance materials and parts. The materials and supplies inventory is primarily acquired for use in future drilling operations or repair operations and is carried at the lower of cost or market, on a first-in, first-out cost basis. "Market," in the context of inventory valuation, represents net realizable value, which is the amount that the Company is allowed to bill to the joint accounts under joint operating agreements to which the Company is a party. Valuation reserve allowances for materials and supplies inventories are recorded as reductions to the carrying values of the materials and supply inventories in the Company's consolidated balance sheets and as other expense in the accompanying consolidated statements of operations. As of December 31, 2011 and 2010, the Company's materials and supplies inventory was net of $0.9 million and $3.6 million, respectively, of valuation reserve allowances. As of December 31, 2011 and 2010, the Company estimated that $60.8 million and $13.7 million, respectively, of its materials and supplies inventory would not be utilized within one year. Accordingly, those inventory values have been classified as other noncurrent assets in the accompanying consolidated balance sheets as of December 31, 2011 and 2010. At December 31, 2010, the Company had inventory totaling $13.6 million classified as discontinued operations held for sale in the accompanying consolidated balance sheets, representing the inventory of Tunisia. At December 31, 2011, the Company had no inventory balance related to Pioneer South Africa.

Commodities inventories are carried at the lower of average cost or market, on a first-in, first-out basis. The Company's commodities inventories consist of oil held in storage and gas pipeline fill volumes. Any valuation allowances of commodities inventories are recorded as reductions to the carrying values of the commodities inventories included in the Company's consolidated balance sheets and as charges to other expense in the consolidated statements of operations.

Oil And Gas Properties

Oil and gas properties.The Company utilizes the successful efforts method of accounting for its oil and gas properties. Under this method, all costs associated with productive wells and nonproductive development wells are capitalized while nonproductive exploration costs and geological and geophysical expenditures are expensed. The Company capitalizes interest on expenditures for significant development projects, generally when the underlying project is sanctioned, until such projects are ready for their intended use. For large development projects requiring significant upfront development costs to support the drilling and production of a planned group of wells, the Company continues to capitalize interest on the portion of the development costs attributable to the planned wells yet to be drilled.

The Company does not carry the costs of drilling an exploratory well as an asset in its consolidated balance sheets following the completion of drilling unless both of the following conditions are met:

(i) The well has found a sufficient quantity of reserves to justify its completion as a producing well.

(ii) The Company is making sufficient progress assessing the reserves and the economic and operating viability of the project.

Due to the capital intensive nature and the geographical location of certain projects, it may take an extended period of time to evaluate the future potential of an exploration project and the economics associated with making a determination on its commercial viability. In these instances, the project's feasibility is not contingent upon price improvements or advances in technology, but rather the Company's ongoing efforts and expenditures related to accurately predicting the hydrocarbon recoverability based on well information, gaining access to other companies' production data in the area, transportation or processing facilities and/or getting partner approval to drill additional appraisal wells. These activities are ongoing and are being pursued constantly. Consequently, the Company's assessment of suspended exploratory well costs is continuous until a decision can be made that the project has found proved reserves to sanction the project or is noncommercial and is charged to exploration and abandonments expense. See Note C for additional information regarding the Company's suspended exploratory well costs.

The Company owns interests in four gas processing plants and ten treating facilities. The Company operates two of the gas processing plants and all ten of the treating facilities. The Company's ownership interests in the gas processing plants and treating facilities is primarily to accommodate handling the Company's gas production and thus are considered a component of the capital and operating costs of the respective fields that they service. To the extent that there is excess capacity at a plant or treating facility, the Company attempts to process third party gas volumes for a fee to keep the plant or treating facility at capacity. All revenues and expenses derived from third party gas volumes processed through the plants and treating facilities are reported as components of oil and gas production costs. Third party revenues generated from the processing plants and treating facilities for the three years ended December 31, 2011, 2010 and 2009 were $46.0 million, $34.0 million and $26.5 million, respectively. Third party expenses attributable to the processing plants and treating facilities for the same respective periods were $22.7 million, $14.3 million and $13.7 million. The capitalized costs of the plants and treating facilities are included in proved oil and gas properties and are depleted using the unit-of-production method along with the other capitalized costs of the field that they service.

Capitalized costs relating to proved properties are depleted using the unit-of-production method based on proved reserves. Costs of significant nonproducing properties, wells in the process of being drilled and development projects are excluded from depletion until such time as the related project is completed and proved reserves are established or, if unsuccessful, impairment is determined.

Proceeds from the sales of individual properties and the capitalized costs of individual properties sold or abandoned are credited and charged, respectively, to accumulated depletion, depreciation and amortization. Generally, no gain or loss is recognized until the entire amortization base is sold. However, gain or loss is recognized from the sale of less than an entire amortization base if the disposition is significant enough to materially impact the depletion rate of the remaining properties in the depletion base.

The Company reviews its long-lived assets to be held and used, including proved oil and gas properties accounted for under the successful efforts method of accounting, whenever events or circumstances indicate that the carrying value of those assets may not be recoverable. An impairment loss is indicated if the sum of the expected future cash flows is less than the carrying amount of the assets. In these circumstances, the Company recognizes an impairment loss for the amount by which the carrying amount of the assets exceeds the estimated fair value of the assets. Estimates of the sum of expected future cash flows requires management to estimate future recoverable proved and risk-adjusted probable and possible reserves, and forecast future commodity prices ("Management's Price Outlook"), production timing, drilling and production cost estimates and discount rates. Management's Price Outlooks represent longer-term outlooks that are developed based on observable third-party futures price outlooks as of a measurement date. Uncertainties about these future cash flow variables cause impairment estimates to be inherently imprecise. See Note R for additional information regarding the Company's impairment assessments.

Unproved oil and gas properties are periodically assessed for impairment on a project-by-project basis. These impairment assessments are affected by the results of exploration activities, commodity price outlooks, planned future sales or expirations of all or a portion of such projects. If the estimated future net cash flows attributable to such projects are not expected to be sufficient to fully recover the costs invested in each project, the Company will recognize an impairment loss at that time.

Goodwill

Goodwill.During 2004, the Company recorded $327.8 million of goodwill associated with a business combination. The goodwill was recorded to the Company's United States reporting unit. The Company has reduced goodwill by $29.7 million since the date of the business combination. The Company reduced the carrying value of goodwill by $10.6 million and $1.3 million during 2010 and 2009, respectively, as a charge to the gain from the sale of a portion of its United States reporting unit. The remaining $17.8 million reduction in goodwill was primarily for tax benefits associated with the exercise of fully-vested stock options assumed in conjunction with the business combination. In accordance with GAAP, goodwill is not amortized to earnings, but is assessed for impairment whenever events or circumstances indicate that impairment of the carrying value of goodwill is likely, but no less often than annually. If the carrying value of goodwill is determined to be impaired, it is reduced for the impaired value with a corresponding charge to pretax earnings in the period in which it is determined to be impaired. During the third quarter of 2011, the Company performed its annual assessment of goodwill for impairment and determined that there was no impairment. See Note R for additional information regarding the Company's impairment assessments.

Other Property And Equipment, Net

Other property and equipment, net.Other property and equipment is recorded at cost. At December 31, 2011 and 2010, respectively, the net carrying value of other property and equipment consisted of $160.8 million and $78.1 million of owned land and buildings, $326.0 million and $155.9 million of heavy equipment and rigs, including drilling rigs, well servicing rigs and fracture stimulation equipment, $28.1 million and $12.9 million of transportation equipment, $34.6 million and $22.3 million of furniture and fixtures, $20.5 million and $14.3 million of leasehold improvements and $3.1 million and nil of other well servicing equipment. At December 31, 2011 and 2010, other property and equipment was net of accumulated depreciation of $297.5 million and $235.3 million, respectively.

The Company's heavy equipment and rigs include assets owned by subsidiaries that provide pumping and well services on Company-operated properties. The primary purposes of the Company's pumping and well services operations are to accommodate the Company's drilling and producing operations by increasing the availability of equipment and services, rather than being limited to third-party availability and to contain services costs. As of December 31, 2011, the Company owns 15 drilling rigs, ten fracture stimulation fleets and other oilfield services equipment, including pulling units, fracture stimulation tanks, water transport trucks, hot oilers, blowout preventers, construction equipment and fishing tools. All intercompany gains or losses of the Company's pumping and well services operations are eliminated. Earnings from providing pumping and well services to third-party working interest owners in Company-operated properties are included in interest and other income in the accompanying consolidated statements of operations.

Equipment items are generally depreciated by individual component on a straight line basis over their economic useful lives, which are generally from two to 12 years. Leasehold improvements are amortized over the lesser of their economic useful lives or the underlying terms of the associated leases.

The Company evaluates other property and equipment for potential impairment whenever indicators of impairment are present. Circumstances that could indicate potential impairment include significant adverse changes in industry trends, economic outlook, legal actions, regulatory changes and significant declines in utilization rates or oil and gas prices. If it is determined that other property and equipment is potentially impaired, the Company performs an impairment evaluation by estimating the future undiscounted net cash flow from the use and eventual disposition of other property and equipment grouped at the lowest level that cash flows can be identified. If the sum of the future undiscounted net cash flows is less than the net book value of the property, an impairment loss is recognized for the excess, if any, of the assets' net book value over its estimated fair value.

Asset Retirement Obligations

Asset retirement obligations. The Company records a liability for the fair value of an asset retirement obligation in the period in which it is incurred if a reasonable estimate of fair value can be made. Asset retirement obligations are generally capitalized as part of the carrying value of the long-lived asset. Conditional asset retirement obligations meet the definition of liabilities and are recognized when incurred if their fair values can be reasonably estimated.

Asset retirement obligation expenditures are classified as cash used in operating activities in the accompanying consolidated statements of cash flows.

Derivatives And Hedging

Derivatives and hedging.All derivatives are recorded in the accompanying consolidated balance sheets at estimated fair value. Effective February 1, 2009, the Company discontinued hedge accounting on all of its then-existing hedge contracts. The effective portions of the discontinued deferred hedges as of February 1, 2009 are included in accumulated other comprehensive income (loss) – net deferred hedge gains (losses), net of tax ("AOCI—Hedging") and are being transferred to earnings during the same periods in which the forecasted hedged transactions are recognized in the Company's earnings. Since February 1, 2009, the Company has recognized changes in the fair values of its derivative contracts as gains or losses in the earnings of the periods in which they occur.

The Company classifies the fair value amounts of derivative assets and liabilities executed under master netting arrangements as net current or noncurrent derivative assets or net current or noncurrent derivative liabilities, whichever the case may be, by commodity and counterparty. Net derivative asset values are determined, in part, by utilization of the derivative counterparties' credit-adjusted risk-free rate curves and net derivative liabilities are determined, in part, by utilization of the Company's and Pioneer Southwest's credit-adjusted risk-free rate curves. The credit-adjusted risk-free rate curves for the Company and the counterparties are based on their independent market-quoted credit default swap rate curves plus the United States Treasury Bill yield curve as of the valuation date. Pioneer Southwest's credit-adjusted risk-free rate curve is based on independent market-quoted forward London Interbank Offered Rate ("LIBOR") curves plus 225 basis points, representing Pioneer Southwest's estimated borrowing rate.

Environmental

Environmental. The Company's environmental expenditures are expensed or capitalized depending on their future economic benefit. Expenditures that relate to an existing condition caused by past operations and that have no future economic benefits are expensed. Expenditures that extend the life of the related property or mitigate or prevent future environmental contamination are capitalized. Liabilities are recorded when environmental assessment and/or remediation is probable and the costs can be reasonably estimated. Such liabilities are undiscounted unless the timing of cash payments for the liability is fixed or reliably determinable. Environmental liabilities normally involve estimates that are subject to revision until settlement occurs.

Treasury Stock

Treasury stock. Treasury stock purchases are recorded at cost. Upon reissuance, the cost of treasury shares held is reduced by the average purchase price per share of the aggregate treasury shares held.

Issuance Of Common Stock

Issuance of common stock.In November 2011, the Company issued 5.5 million shares of its common stock and realized $484.2 million of proceeds, net of associated offering costs.

Revenue Recognition

Revenue recognition.The Company does not recognize revenues until they are realized or realizable and earned. Revenues are considered realized or realizable and earned when: (i) persuasive evidence of an arrangement exists, (ii) delivery has occurred or services have been rendered, (iii) the seller's price to the buyer is fixed or determinable and (iv) collectability is reasonably assured.

The Company uses the entitlements method of accounting for oil, natural gas liquids ("NGL") and gas revenues. Sales proceeds in excess of the Company's entitlement are included in other liabilities and the Company's share of sales taken by others is included in other assets in the accompanying consolidated balance sheets.

The Company had no material oil entitlement assets or NGL entitlement assets or liabilities as of December 31, 2011 or 2010. The following table presents the Company's oil entitlement liabilities and gas entitlement assets and liabilities with their associated volumes as of December 31, 2011 and 2010:

	December 31,
	2011				2010
	Amount		Volume		Amount		Volume
	(dollars in millions)
Oil entitlement liabilities (volumes in MBbls)	$	—		—	$	1.2		13
Gas entitlement assets (volumes in MMcf)	$	7.6		3,024	$	7.6		3,015
Gas entitlement liabilities (volumes in MMcf)	$	2.6		650	$	1.6		439

Stock-Based Compensation

Stock-based compensation.For stock-based compensation awards granted or modified, compensation expense is being recognized in the Company's financial statements on a straight line basis over the awards' vesting periods based on their fair values on the dates of grant. The stock-based compensation awards vest over a period not exceeding three years. The amount of compensation expense recognized at any date is at least equal to the portion of the grant date value of the award that is vested at that date. The Company utilizes (i) the Black-Scholes option pricing model to measure the fair value of stock options, (ii) the prior day's closing stock price on the date of grant for the fair value of restricted stock, restricted stock units, partnership unit awards or phantom unit awards that are expected to be settled in the Company's common stock or Pioneer Southwest common units ("Equity Awards"), (iii) the Monte Carlo simulation method for the fair value of performance unit awards and (iv) a probabilistic forecasted fair value method for Series B unit awards issued by Sendero.

Stock-based compensation liability awards are awards that are expected to be settled in cash on their vesting dates, rather than in equity shares or units ("Liability Awards"). Stock-based Liability Awards are recorded as accounts payable—affiliates based on the vested portion of the fair value of the awards on the balance sheet date. The fair values of Liability Awards are updated at each balance sheet date and changes in the fair values of the vested portions of the awards are recorded as increases or decreases to compensation expense.