2.2.0.25falsefalse1310 - Disclosure - Summary of Significant Accounting Policies (Policies)truefalsefalse1falsefalseUSDfalsefalse1/1/2010 - 12/31/2010 USD ($) / shares USD ($) $FROM_Jan01_2010_TO_Dec31_2010http://www.sec.gov/CIK0000773910duration2010-01-01T00:00:002010-12-31T00:00:00usdPerShrDividehttp://www.xbrl.org/2003/iso4217USDiso4217http://www.xbrl.org/2003/instancesharesxbrli0USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170PureStandardhttp://www.xbrl.org/2003/instancepurexbrli0SharesStandardhttp://www.xbrl.org/2003/instancesharesxbrli0MMboeStandardhttp://www.anadarko.com/20101231MMboeapc0USDUSD$5false0apc_GeneralTextBlockapcfalsenadurationDescribes the nature of an entity's business and the major services it provides.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00General   Anadarko Petroleum Corporation is engaged in the exploration, development, production and marketing of natural gas, crude oil, condensate and natural gas liquids (NGLs). The Company also engages in the gathering, processing, and treating of natural gas, and transporting natural gas, crude oil and NGLs. The Company also participates in the hard minerals business through its ownership of non-operated joint ventures and royalty arrangements. The terms “Anadarko” and “Company” refer to Anadarko Petroleum Corporation and its consolidated subsidiaries.General   Anadarko Petroleum Corporation is engaged in the exploration, development, production and marketing of natural gas, crude oil,falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringDescribes the nature of an entity's business and the major services it provides.No authoritative reference available.falsefalseGeneral6false0apc_BasisOfPresentationTextBlockapcfalsenadurationDisclosure related to the basis of presentation of financial statements and use of estimates.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00Basis of Presentation   The Consolidated Financial Statements have been prepared in conformity with accounting principles generally accepted in the United States. The Consolidated Financial Statements include the accounts of Anadarko and entities in which it holds a controlling interest. All intercompany transactions have been eliminated. Undivided interests in oil and natural-gas exploration and production joint ventures are consolidated on a proportionate basis. Investments in non-controlled entities over which Anadarko has the ability to exercise significant influence over operating and financial policies, are accounted for using the equity method. In applying the equity method of accounting, the investments are initially recognized at cost, and subsequently adjusted for the Company's proportionate share of earnings and losses and distributions. Other investments are carried at original cost. Investments accounted for using the equity- and cost-method are reported as a component of other assets. Certain prior-period amounts have been reclassified to conform to the current-year presentation.Basis of Presentation   The Consolidated Financial Statements have been prepared in conformity with accounting principles generally accepted infalsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringDisclosure related to the basis of presentation of financial statements and use of estimates.No authoritative reference available.falsefalseBasis of Presentation7false0apc_UseOfEstimatesPolicyTextBlockapcfalsenadurationProvides an entity's explanation that the preparation of financial statements in conformity with generally accepted...falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00Use of Estimates   In preparing financial statements in accordance with accounting principles generally accepted in the United States, management makes informed judgments and estimates that affect the reported amounts of assets and liabilities as of the date of the financial statements and the reported amounts of revenues and expenses during the periods reported. Management evaluates its estimates and related assumptions regularly, including those related to the value of properties and equipment, proved reserves, goodwill, intangible assets, asset retirement obligations, litigation reserves, environmental liabilities, pension assets and liabilities and costs, income taxes, and fair values. Changes in facts and circumstances or additional information may result in revised estimates and actual results may differ from these estimates.Use of Estimates   In preparing financial statements in accordance with accounting principles generally accepted in the United States,falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringProvides an entity's explanation that the preparation of financial statements in conformity with generally accepted accounting principles requires the use of management estimates. Estimates used in the determination of carrying amounts of assets or liabilities, or in disclosure of gain or loss contingencies should be disclosed if known information available prior to issuance of the financial statements indicates that both of these criteria are met: (1) It is at least reasonably possible that the estimate of the effect on the financial statements of a condition, situation, or set of circumstances that existed at the date of the financial statements will change in the near term (less than one year from the date of issuance) due to one or more future confirming events, and (2) The effect of the change would be material to the financial statements. The disclosure should indicate the nature of the uncertainty and include an indication that it is at least reasonably possible that a change in the estimate will occur in the near term. Disclosure of the factors that cause the estimate to be sensitive to change also is encouraged. Entities also may identify those areas that are subject to significant estimates.No authoritative reference available.falsefalseUse of Estimates8false0apc_FairValuePolicyTextBlockapcfalsenadurationDescribes an entity's accounting policy for determining the fair value of its assets and liabilities.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00Fair Value   Fair value is defined as the price that would be received to sell an asset or the price paid to transfer a liability in an orderly transaction between market participants at the measurement date. Inputs used in determining fair value are characterized according to a hierarchy that prioritizes those inputs based on the degree to which they are observable. The three input levels of the fair-value hierarchy are as follows: Level 1—Inputs represent quoted prices in active markets for identical assets or liabilities (for example, exchange-traded commodity derivatives). Level 2—Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly (for example, quoted market prices for similar assets or liabilities in active markets or quoted market prices for identical assets or liabilities in markets not considered to be active, inputs other than quoted prices that are observable for the asset or liability, or market-corroborated inputs). Level 3—Inputs that are not observable from objective sources, such as the Company's internally developed assumptions used in pricing an asset or liability (for example, an estimate of future cash flows used in the Company's internally developed present value of future cash flows model that underlies the fair-value measurement).       In determining fair value, the Company utilizes observable market data when available, or models that incorporate observable market data. In addition to market information, the Company incorporates transaction-specific details that, in management's judgment, market participants would take into account in measuring fair value.        In arriving at fair-value estimates, the Company utilizes the most observable inputs available for the valuation technique employed. If a fair-value measurement reflects inputs at multiple levels within the hierarchy, the fair-value measurement is characterized based on the lowest level of input that is significant to the fair-value measurement. For Anadarko, recurring fair-value measurements are performed for interest-rate derivatives, commodity derivatives and investments in trading securities.        The carrying amount of cash and cash equivalents, accounts receivable and accounts payable reported on the Consolidated Balance Sheets approximates fair value. The fair value of debt is the estimated amount the Company would have to pay to repurchase its debt, including any premium or discount attributable to the difference between the stated interest rate and market rate of interest at each balance sheet date. Debt fair values, as disclosed in Note 11, are based on quoted market prices for identical instruments, if available, or based on valuations of similar debt instruments.       Non-financial assets and liabilities initially measured at fair value include certain assets and liabilities acquired in a business combination or through a non-monetary exchange transaction, intangible assets and goodwill, asset retirement obligations and exit or disposal costs, and capital lease assets where the present value of lease payments is greater than the fair value of the leased asset.Fair Value   Fair value is defined as the price that would be received to sell an asset or the price paid to transfer a liability in an orderlyfalsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringDescribes an entity's accounting policy for determining the fair value of its assets and liabilities.No authoritative reference available.falsefalseFair value9false0us-gaap_RevenueRecognitionPolicyTextBlockus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00Revenues   The Company's natural gas is sold primarily to interstate and intrastate natural-gas pipelines, direct end-users, industrial users, local distribution companies and natural-gas marketers. Crude oil and condensate are sold primarily to marketers, gatherers and refiners. NGLs are sold primarily to direct end-users, refiners and marketers. The majority of the Company's receivables are paid within two months following the month of purchase. In 2010, 2009 and 2008, there were no sales to individual customers that exceeded 10% of the Company's total sales revenues.       The Company recognizes sales revenues for natural gas, oil and condensate, and NGLs based on the amount of each product sold to purchasers when delivery to the purchaser has occurred and title has transferred. This occurs when product has been delivered to a pipeline or a tanker lifting has occurred. The Company follows the sales method of accounting for natural-gas production imbalances. If the Company's sales volumes for a well exceed the estimated remaining recoverable reserves of the well, a liability is recognized. No receivables are recorded for those wells on which the Company has taken less than its proportionate share of production.        The Company enters into buy/sell arrangements for a portion of its crude-oil production. Under these arrangements, barrels are sold at prevailing market prices at a location, and in an additional transaction entered into in contemplation of the sale transaction with the same third party, barrels are re-purchased at a different location at the market prices prevailing at that location. The barrels are then sold at prevailing market prices at the re-purchase location. These arrangements are often required by private transporters. In these transactions, the re-purchase price is more than the original sales price with the difference representing a transportation fee. Other buy/sell arrangements are entered in order to shift the ultimate sales point of the Company's production to a more liquid location, thereby avoiding potential marketing fees and other market-price reductions. In these transactions, the sales price in the field and the re-purchase price are each at prevailing market prices at the respective locations. Anadarko uses these buy/sell arrangements in its marketing and trading activities and, as such, reports these transactions in the Consolidated Statements of Income on a net basis.        Anadarko provides gathering, processing, treating and transportation services pursuant to a variety of contracts. Under these arrangements, the Company receives fees, or retains a percentage of products or a percentage of the proceeds from the sale of products and recognizes revenue at the time the services are performed or product is sold. These revenues are included in gathering, processing and marketing sales.       Marketing margins related to the Company's production are included in natural-gas sales, oil and condensate sales, and NGLs sales. Marketing margins related to sales of commodities purchased from third parties, as well as realized and unrealized gains and losses on such marketing activities, are included in gathering, processing and marketing sales.Revenues   The Company's natural gas is sold primarily to interstate and intrastate natural-gas pipelines, direct end-users, industrial users,falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringDescribes an entity's accounting policy for revenue recognition. If the entity has different policies for different types of revenue transactions, the policy for each material type of transaction should be disclosed. If a sales transaction has multiple element arrangements (for example, delivery of multiple products, services or the rights to use assets) the disclosure may indicate the accounting policy for each unit of accounting as well as how units of accounting are determined and valued. The disclosure may encompass important judgment as to appropriateness of principles related to recognition of revenue. The disclosure also may indicate the entity's treatment of any unearned or deferred revenue that arises from the transaction.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 13 -Section B -Paragraph Question 1 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 22 -Paragraph 8, 12, 13 falsefalseRevenues10false0us-gaap_CashAndCashEquivalentsPolicyTextBlockus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00Cash Equivalents   The Company considers all highly liquid investments with a maturity of three months or less when purchased to be cash equivalents.Cash Equivalents   The Company considers all highly liquid investments with a maturity of three months or less when purchased to be cashfalsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringA description of a company's cash and cash equivalents accounting policy. An entity shall disclose its policy for determining which items are treated as cash equivalents. Other information that may be disclosed includes (1) the nature of any restrictions on the entity's use of its cash and cash equivalents, (2) whether the entity's cash and cash equivalents are insured or expose the entity to credit risk, (3) the classification of any negative balance accounts (overdrafts), and (4) the carrying basis of cash equivalents (for example, at cost) and whether the carrying amount of cash equivalents approximates fair value. Cash includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the customer may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. In addition, cash equivalents include short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months. For a bank, may include explanation and amount of requirement to maintain reserves against deposits.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Financial Reporting Release (FRR) -Number 203 -Paragraph 02-03 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 1 -Article 5 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 7, 8, 9, 10 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Technical Practice Aid (TPA) -Number 2110 -Paragraph 6 falsefalseCash Equivalents11false0us-gaap_ReceivablesPolicyTextBlockus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00Allowance for Uncollectible Accounts   The Company conducts credit analyses of customers prior to making any sales to new customers or increasing credit for existing customers. Based on these analyses, the Company may require a standby letter of credit or a financial guarantee. The Company charges uncollectible accounts receivable against the allowance for uncollectible accounts when it determines collection will no longer be pursued. At December 31, 2010 and 2009, accounts receivable are shown net of allowance for uncollectible accounts of $9 million and $11 million, respectively.Allowance for Uncollectible Accounts   The Company conducts credit analyses of customers prior to making any sales to new customers orfalsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringDescribes an entity's accounting policy for trade and other accounts receivable, and finance, loan and lease receivables, including those classified as held for investment and held for sale. This disclosure may include (1) the basis at which such receivables are carried in the entity's statements of financial position (2) how the level of the valuation allowance for receivables is determined (3) when impairments, charge-offs or recoveries are recognized for such receivables (4) the treatment of origination fees and costs, including the amortization method for net deferred fees or costs (5) the treatment of any premiums or discounts or unearned income (6) the entity's income recognition policies for such receivables, including those that are impaired, past due or placed on nonaccrual status and (7) the treatment of foreclosures or repossessions (8) the nature and amount of any guarantees to repurchase receivables.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 3-5 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 114 -Paragraph 20 -Subparagraph b Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Emerging Issues Task Force (EITF) -Number 92-5 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Statement of Position (SOP) -Number 01-6 -Paragraph 13 falsefalseAllowance for Accounts Receivable12false0us-gaap_InventoryPolicyTextBlockus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00Inventories   Commodity inventories are stated at the lower of average cost or market.Inventories   Commodity inventories are stated at the lower of average cost or market.falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringDescribes an entity's accounting policies covering its major classes of inventories, bases of stating inventories (for example lower of cost or market), methods by which amounts are added and removed from inventory classes (for example FIFO, LIFO, or average cost), loss recognition on impairment of inventories, and situations in which inventories are stated above cost. If inventory is carried at cost, this description includes the nature of the cost elements included in inventory.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Financial Reporting Release (FRR) -Number 206 -Chapter 2 -Paragraph b -Subparagraph i, ii Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 43 -Chapter 4 -Paragraph 3, 5-10, 15, 16, 17 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 6 -Subparagraph a -Article 5 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 43 -Chapter 3 -Section A -Paragraph 9 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Statement of Position (SOP) -Number 81-1 -Paragraph 69-75 falsefalseInventories13false0us-gaap_PropertyPlantAndEquipmentPolicyTextBlockus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00Properties and Equipment   Properties and equipment are stated at cost less accumulated depreciation, depletion and amortization expense (DD&A). Costs of improvements that appreciably improve the efficiency or productive capacity of existing properties or extend their lives are capitalized. Maintenance and repairs are expensed as incurred. Upon retirement or sale, the cost of properties and equipment, net of the related accumulated DD&A, is removed and, if appropriate, gain or loss is recognized in gains (losses) on divestitures and other, net.  Oil and Gas Properties   The Company applies the successful efforts method of accounting for oil and gas properties. Exploration costs such as exploratory geological and geophysical costs, delay rentals and exploration overhead are charged against earnings as incurred. Acquisition costs and costs of drilling exploratory wells are capitalized pending determination of whether proved reserves can be attributed to the area as a result of drilling the well. If management determines that commercial quantities of hydrocarbons have not been discovered, capitalized costs associated with exploratory wells are charged to exploration expense. Acquisition costs of unproved properties are assessed for impairment during the holding period and transferred to proved oil and gas properties to the extent the costs are associated with successful exploration activities. Significant undeveloped leases are assessed individually for impairment, based on the Company's current exploration plans, and a valuation allowance is provided if impairment is indicated. Unproved oil and gas properties with individually insignificant lease acquisition costs are amortized on a group basis (thereby establishing a valuation allowance) over the average terms of the leases, at rates that provide for full amortization of unsuccessful leases upon lease expiration or abandonment. Costs of expired or abandoned leases are charged against the valuation allowance, while costs of productive leases are transferred to proved oil and gas properties. Costs of maintaining and retaining unproved properties, as well as amortization of individually insignificant leases and impairment of unsuccessful leases, are included in exploration expense.  Capitalized Interest   Interest is capitalized as part of the historical cost of developing and constructing assets for significant projects. Significant oil and gas investments in unproved properties, significant exploration and development projects for which DD&A is not currently recognized, and exploration or development activities that are in progress qualify for interest capitalization. Interest is capitalized until the asset is ready for service. Capitalized interest is determined by multiplying the Company's weighted-average borrowing cost on debt by the average amount of qualifying costs incurred. Once an asset subject to interest capitalization is completed and placed in service, the associated capitalized interest is expensed through depreciation or impairment, along with other capitalized costs related to that asset.Asset Retirement Obligations   Asset retirement obligations (AROs) associated with the retirement of tangible long-lived assets are recognized as liabilities with an increase to the carrying amounts of the related long-lived assets in the period incurred. The cost of the tangible asset, including the asset retirement cost, is depreciated over the useful life of the asset. AROs are recorded at estimated fair value, measured by reference to the expected future cash outflows required to satisfy the retirement obligations discounted at the Company's credit-adjusted risk-free interest rate. Accretion expense is recognized over time as the discounted liabilities are accreted to their expected settlement value. If estimated future costs of AROs change, an adjustment is recorded to both the asset retirement obligation and the long-lived asset. Revisions to estimated AROs can result from changes in retirement cost estimates, revisions to estimated inflation rates and changes in the estimated timing of abandonment.  Impairments   Properties and equipment, net of salvage value, are reviewed for impairment at the lowest level for which identifiable cash flows are independent of cash flows from other assets, and when facts and circumstances indicate that net book values may not be recoverable. In performing this review, an undiscounted cash flow test is performed on the impairment unit. If the sum of the undiscounted estimated future 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 property's net book value over its estimated fair value.  Depreciation, Depletion and Amortization   Costs of drilling and equipping successful wells, costs to construct or acquire facilities other than offshore platforms and associated asset retirement costs are depreciated using the unit-of-production (UOP) method based on total estimated proved developed oil and gas reserves. Costs of acquiring proved properties, including leasehold acquisition costs transferred from unproved properties and costs to construct or acquire offshore platforms and associated asset retirement costs, are depleted using the UOP method based on total estimated proved developed and undeveloped reserves. Mineral properties are also depleted using the UOP method. All other properties are stated at historical acquisition cost, net of impairments, and depreciated using the straight-line method over the useful lives of the assets, which range from 3 to 15 years for furniture and equipment, up to 40 years for buildings, and up to 47 years for gathering facilities.Properties and Equipment   Properties and equipment are stated at cost less accumulated depreciation, depletion and amortization expensefalsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringDescribes an entity's accounting policy for property, plant and equipment which may include the basis of such assets, depreciation methods used and estimated useful lives, the entity's capitalization policy, including its accounting treatment for costs incurred for repairs and maintenance activities, whether such asset balances include capitalized interest and the method by which such is calculated, how disposals of such assets are accounted for and how impairment of such assets is assessed and recognized.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 43 -Chapter 9 -Section C -Paragraph 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 144 -Paragraph 7 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 22 -Paragraph 12, 13 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 34 -Paragraph 8, 9 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 13 -Subparagraph a -Article 5 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 5 -Subparagraph d falsefalseProperties and Equipment14false0us-gaap_GoodwillAndIntangibleAssetsPolicyTextBlockus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00Goodwill and Other Intangible Assets   The Company tests goodwill for impairment annually, or more often as facts and circumstances warrant. During 2009, the Company changed its annual goodwill impairment testing date from January 1 to October 1, to ensure the completion of the annual goodwill impairment test prior to the end of the annual reporting period, and to align impairment testing procedures with year-end financial reporting. Changes in goodwill may result from, among other things, impairments, future acquisitions or future divestitures. See Note 6.       Other intangible assets represent contractual rights obtained in connection with a business combination that had favorable contractual terms relative to market at the acquisition date. Other intangible assets are amortized over their estimated useful lives and are reviewed for impairment whenever impairment indicators are present. See Note 6.Goodwill and Other Intangible Assets   The Company tests goodwill for impairment annually, or more often as facts and circumstances warrant.falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringDescribes an entity's accounting policy for goodwill and intangible assets. This accounting policy also may address how an entity assesses and measures impairment of goodwill and intangible assets.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 144 -Paragraph 7-18, 22 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 142 -Paragraph 4, 11-23, 26, 34 falsefalseGoodwill and Other Intangible Assets15false0us-gaap_DerivativesPolicyTextBlockus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00Derivative Instruments   Anadarko uses derivative instruments to manage its exposure to cash-flow variability resulting from commodity price and interest-rate risk. All derivatives that do not satisfy the normal purchases and sales exception criteria are carried on the balance sheet at fair value and are included in other current assets, other assets, accrued expenses or other long-term liabilities, depending on the derivative position and the expected timing of settlement. Where the Company has the contractual right and intends to net settle, derivative assets and liabilities are reported on a net basis.       Realized and unrealized gains and losses on derivative instruments are recognized on a current basis. Net derivative losses attributable to derivatives previously subject to hedge accounting reside in accumulated other comprehensive income and will be reclassified to earnings in future periods as the economic transactions to which the derivatives relate affect earnings. See Note 9.Derivative Instruments   Anadarko uses derivative instruments to manage its exposure to cash-flow variability resulting from commodity price andfalsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringDescribes an entity's accounting policies for its derivative instruments and hedging activities. Disclosure may include: (1) Each method used to account for derivative financial instruments and derivative commodity instruments ("derivatives"); (2) the types of derivatives accounted for under each method; (3) the criteria required to be met for each accounting method used, including a discussion of the criteria required to be met for hedge or deferral accounting and accrual or settlement accounting (for example: whether and how risk reduction, correlation, designation, and effectiveness tests are applied); (4) the accounting method used if the criteria specified for hedge accounting are not met; (5) the method used to account for termination of derivatives designated as hedges or derivatives used to affect directly or indirectly the terms, fair values, or cash flows of a designated item; (6) the method used to account for derivatives when the designated item matures, is sold, is extinguished, or is terminated. In addition, the method used to account for derivatives designated to an anticipated transaction, when the anticipated transaction is no longer likely to occur; and (7) where and when derivatives, and their related gains (losses) are reported in the statement of financial position, cash flows, and results of operations and (8) an accounting policy decision to offset fair value amounts with counterparties. An entity should also consider describing its embedded derivatives, and the method(s) used to determine the fair values of derivatives and any significant assumptions used in such valuations.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 44 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 08 -Paragraph n -Article 4 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Interpretation (FIN) -Number 39 -Paragraph 10 falsefalseDerivative Instruments16false0apc_AccountsPayablePolicyTextBlockapcfalsenadurationDescribes the entity's accounting policies for accounts payable.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00Accounts Payable   Included in accounts payable at December 31, 2010 and 2009, are liabilities of $259 million and $252 million, respectively, representing the amount by which checks issued, but not presented to the Company's banks for collection, exceed balances in applicable bank accounts, and changes in these liabilities are reflected in cash flows from financing activities.Accounts Payable   Included in accounts payable at December 31, 2010 and 2009, are liabilities of $259 million and $252 million,falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringDescribes the entity's accounting policies for accounts payable.No authoritative reference available.falsefalseAccounts Payable17false0us-gaap_LegalCostsPolicyTextBlockus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00Legal Contingencies   The Company is subject to legal proceedings, claims and liabilities that arise in the ordinary course of its business. Except for legal contingencies acquired in a business combination, which are recorded at fair value, the Company accrues losses associated with legal claims when such losses are probable and reasonably estimable. Estimates are adjusted as additional information becomes available or circumstances change. Legal defense costs associated with loss contingencies are expensed in the period incurred. See Note 2 and Note 15.Legal Contingencies   The Company is subject to legal proceedings, claims and liabilities that arise in the ordinary course of its business.falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringDescribes an entity's accounting policy for legal costs incurred to protect or defend the entity's assets and rights, or to obtain assets, including monetary damages, or to obtain rights.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 22 -Paragraph 8 falsefalseLegal Contingencies18false0apc_EnvironmentalContingenciesTextBlockapcfalsenadurationDescribes the accounting policy for (1) legal obligations associated with the disposal or removal of a long-lived asset from...falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00Environmental Contingencies   Except for environmental contingencies acquired in a business combination, which are recorded at fair value, the Company accrues losses associated with environmental obligations when such losses are probable and can be reasonably estimated. Accruals for estimated environmental losses are recognized no later than at the time the remediation feasibility study, or the evaluation of response options, is complete. These accruals are adjusted as additional information becomes available or as circumstances change. Future environmental expenditures are not discounted to their present value. Recoveries of environmental costs from other parties are recorded separately as assets at their undiscounted value when receipt of such recoveries is probable. See Note 2 and Note 15.Environmental Contingencies   Except for environmental contingencies acquired in a business combination, which are recorded at fair value, thefalsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringDescribes the accounting policy for (1) legal obligations associated with the disposal or removal of a long-lived asset from service that result from the acquisition, construction, or development or from the normal operation of a long-lived asset; and (2) certain environmental remediation liabilities that resulted from the improper or other-than-normal operation of a long-lived asset. This accounting policy may address (1) whether the related remediation costs are expensed or capitalized, (2) whether the obligation is measured on a discounted basis, (3) the event, situation, or set of circumstances that generally triggers recognition of loss contingencies arising from the entity's environmental remediation-related obligations, and (4) the timing of recognition of any recoveries.No authoritative reference available.falsefalseEnvironmental Contingencies19false0apc_PensionPlansOtherPostretirementBenefitsAndEmployeeSavingsPlansPolicyTextBlockapcfalsenadurationDescribes an entity's accounting policy for its pension plans, other postretirement benefits and employee savings plans. This...falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00Pension Plans, Other Postretirement Benefits and Defined-Contribution Plans   The Company measures pension plan assets at fair value. Defined-benefit plan obligations and costs are actuarially determined, incorporating the use of various assumptions. Critical assumptions for pension and other postretirement plans include the discount rate, the expected rate of return on plan assets (for funded pension plans), the rate of future compensation increases and the health care cost trend rate. Other assumptions involve demographic factors such as retirement, mortality and turnover. The Company evaluates and updates its actuarial assumptions at least annually. See Note 20.Pension Plans, Other Postretirement Benefits and Defined-Contribution Plans   The Company measures pension plan assets at fair value.falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringDescribes an entity's accounting policy for its pension plans, other postretirement benefits and employee savings plans. This disclosure may address (1) the types of plans sponsored by the entity, and the benefits provided by each plan (2) groups that participate in (or are covered by) each plan (3) how plan assets, liabilities and expenses are measured, including the use of any actuaries and (4) significant assumptions used by the entity to value plan assets and liabilities and how such assumptions are derived.No authoritative reference available.falsefalsePension Plans, Other Postretirement Benefits and Defined-Contribution Plans20false0apc_NoncontrollingInterestPolicyTextBlockapcfalsenadurationDescribes the entity's accounting policies for noncontrolling interests.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00Noncontrolling Interests   Noncontrolling interests represent third-party ownership in the net assets of the Company's consolidated subsidiaries and are presented as a component of equity. Changes in Anadarko's ownership interests in subsidiaries that do not result in deconsolidation are recognized in equity. See Note 7.Noncontrolling Interests   Noncontrolling interests represent third-party ownership in the net assets of the Company's consolidated subsidiariesfalsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringDescribes the entity's accounting policies for noncontrolling interests.No authoritative reference available.falsefalseNoncontrolling Interests21false0us-gaap_IncomeTaxPolicyTextBlockus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00Income Taxes   The Company files various United States federal, state and foreign income tax returns. Deferred federal, state and foreign income taxes are provided on temporary differences between the financial statement carrying amounts of assets and liabilities and their respective tax bases. The Company recognizes a tax benefit from an uncertain tax position when it is more likely than not that the position will be sustained upon examination, based on the technical merits of the position. The tax benefit recorded is equal to the largest amount that is greater than 50% likely to be realized through final settlement with a taxing authority. See Note 17.Income Taxes   The Company files various United States federal, state and foreign income tax returns. Deferred federal, state and foreign incomefalsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringDescribes an entity's accounting policy for income taxes, which may include its accounting policies for recognizing and measuring deferred tax assets and liabilities and related valuation allowances, recognizing investment tax credits, operating loss carryforwards, tax credit carryforwards, and other carryforwards, methodologies for determining its effective income tax rate and the characterization of interest and penalties in the financial statements.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 4 -Paragraph 11 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Interpretation (FIN) -Number 48 -Paragraph 20 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 109 -Paragraph 6-34, 43, 47, 49 falsefalseIncome Taxes22false0apc_ShareBasedCompensationPolicyTextBlockapcfalsenadurationThis element describes an entity's accounting policy for stock option and stock incentive plans. This disclosure may include...falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00Share-Based Compensation   The Company accounts for share-based compensation at fair value. The Company grants equity-classified awards including stock options and non-vested equity shares (restricted stock awards and units). The Company also grants equity-classified and liability-classified awards based on a comparison of the Company's total shareholder return (TSR) to the TSR of a predetermined group of peer companies (performance units).       The fair value of stock option awards is determined on the date of grant using the Black-Scholes option-pricing model. Restricted stock awards and units are valued using the market price of Anadarko common stock on the grant date. For equity- and liability-classified performance units, fair value is determined using a Monte Carlo simulation.       The Company records compensation cost, net of estimated forfeitures, for share-based compensation awards over the requisite service period. As each award of stock options or non-vested equity shares vests, an adjustment is made to compensation cost for any difference between the estimated forfeitures and the actual forfeitures related to the vested awards. For share-based awards that contain service conditions, compensation cost is recorded using the straight-line method. If the requisite service period is satisfied, compensation cost is not adjusted. For liability-classified performance units, expense is recognized only for those awards that ultimately vest using the market price of Anadarko common stock on the date the awards are earned. See Note 13.Share-Based Compensation   The Company accounts for share-based compensation at fair value. The Company grants equity-classified awardsfalsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringThis element describes an entity's accounting policy for stock option and stock incentive plans. This disclosure may include (1) the types of stock option or incentive plans sponsored by the entity (2) the groups that participate in (or are covered by) each plan (3) significant plan provisions and (4) how stock compensation is measured, and the methodologies and significant assumptions used to determine that measurement.No authoritative reference available.falsefalseShare-Based Compensation23false0us-gaap_DiscontinuedOperationsPolicyTextBlockus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00Discontinued Operations   In November 2006, Anadarko sold its wholly owned subsidiary, Anadarko Canada Corporation. The results of the Company's Canadian operations have been classified as discontinued operations in the Consolidated Statements of Income and Consolidated Statements of Cash Flows for 2008 and primarily relate to adjustments to an indemnity obligation provided by the Company to the purchaser, as well as expenses associated with finalizing exit activities. Unless otherwise indicated, information presented in the Notes to Consolidated Financial Statements relates only to Anadarko's continuing operations. See Note 15.Discontinued Operations   In November 2006, Anadarko sold its wholly owned subsidiary, Anadarko Canada Corporation. The results of the Company'sfalsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringDescribes an entity's accounting policy for any discontinued operations. The results of operations of a component of an entity that either has been disposed of or is classified as held for sale shall be reported in discontinued operations if both: (a) the operations and cash flows of the component have been (or will be) eliminated from the ongoing operations of the entity as a result of the disposal transaction and (b) the entity will not have any significant continuing involvement in the operations of the component after the disposal transaction. If the entity elects to allocate interest expense to a discontinued operation, it should disclose its accounting policy for this election and describe its method of allocation.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Emerging Issues Task Force (EITF) -Number 03-13 -Paragraph 17 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Emerging Issues Task Force (EITF) -Number 87-24 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 144 -Paragraph 41, 42, 43, 44 falsefalseDiscontinued Operations24false0us-gaap_EarningsPerSharePolicyTextBlockus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00Earnings Per Share   The Company's basic earnings per share (EPS) amounts have been computed based on the average number of shares of common stock outstanding for the period and include the effect of any participating securities as appropriate. Diluted EPS includes the effect of the Company's outstanding stock options, restricted stock awards, restricted stock units and performance-based stock awards if the inclusion of these items is dilutive. See Note 12.Earnings Per Share   The Company's basic earnings per share (EPS) amounts have been computed based on the average number of shares of commonfalsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringDiscloses the methodology and assumptions used to compute basic and diluted earnings (loss) per share for each class of common stock and participating security. Addresses all significant policy factors, including any antidilutive items that have been excluded from the computation and takes into account stock dividends, splits and reverse splits that occur after the balance sheet date of the latest reporting period but before the issuance of the financial statements.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 128 -Paragraph 40 -Subparagraph a Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 128 -Paragraph 6, 8-16, 60 falsefalseEarnings Per Share25false0us-gaap_ScheduleOfNewAccountingPronouncementsAndChangesInAccountingPrinciplesTextBlockus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00Changes in Accounting Principles   The Company adopted a new fair-value measurement standard on January 1, 2008. The standard defines fair value, establishes a framework for measuring fair value under existing accounting pronouncements that require fair-value measurements and expands fair-value measurement disclosures. The Company elected to implement the standard with the one-year deferral permitted for non-financial assets and non-financial liabilities, except those non-financial items recognized or disclosed at fair value on a recurring basis (at least annually). The deferral period ended on January 1, 2009, and the Company began applying the fair-value framework to non-financial assets and non-financial liabilities initially measured at fair value, such as assets and liabilities acquired in a business combination, impaired long-lived assets (asset groups), intangible assets and goodwill, asset retirement obligations and exit or disposal costs, and certain capital lease assets.       Effective January 1, 2010, the Company adopted revised oil and gas reserve estimation standards. This standard allows the use of reliable technology in determining estimates of proved reserve quantities and requires the use of a 12-month first-day-of-the-month average price to estimate proved reserves. Adoption of this standard did not have a material impact on depreciation, depletion and amortization expense.Changes in Accounting Principles   The Company adopted a new fair-value measurement standard on January 1, 2008. The standard definesfalsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringRepresents disclosure of any changes in an accounting principle, including a change from one generally accepted accounting principle to another generally accepted accounting principle when there are two or more generally accepted accounting principles that apply or when the accounting principle formerly used is no longer generally accepted. Also disclose any change in the method of applying an accounting principle, or any change in an accounting principle required by a new pronouncement in the unusual instance that a new pronouncement does not include specific transition provisions.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 154 -Paragraph 2, 17, 18 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 28 -Paragraph 23, 24 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 01 -Paragraph b -Subparagraph 6 -Article 10 falsefalseChanges in Accounting Principles26false0apc_DefinedBenefitPlanAssumptionsUsedInCalculationsPolicyTextBlockapcfalsenadurationDescription and explanation of the assumptions (including assumed discount rates, rates of compensation increase, and...falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00       The discount-rate assumption used by the Company represents an estimate of the interest rate at which the pension and other postretirement obligations could effectively be settled on the measurement date. The Company currently uses a yield-curve analysis to support the discount-rate assumption for the plans. This analysis involves the creation of a hypothetical Aa spot yield curve represented by a series of high-quality, non-callable, marketable bonds, and discounting the estimated cash flows associated with benefits to be provided under each plan using interest rates on the curve that correspond to the expected timing of payment. The present value of future plan benefits determined in this manner is then used to estimate a single plan-specific discount rate that equates such present value with the corresponding future undiscounted cash flows. Application of this method resulted in a weighted-average discount-rate assumption (weighted by the plan-level benefit obligation) at December 31, 2010, of 4.75% for pension plans and 5.25% for other postretirement plans.       The discount-rate assumption used by the Company represents an estimate of the interest rate at which the pension andfalsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringDescription and explanation of the assumptions (including assumed discount rates, rates of compensation increase, and expected long-term rates of return on plan assets) used to calculate the benefit obligation and the assumptions used to calculate net periodic benefit cost. May also include other assumptions such as market-related value, average remaining service period, and average remaining life expectancy.No authoritative reference available.falsefalseDefined Benefit Plan Weighted Average Assumptions Used in Calculations27false0apc_DefinedBenefitPlanInvestmentPoliciesTextBlockapcfalsenadurationDefined benefit plan investment policies disclosure.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00Investment Policies and Strategies   The Company has adopted a balanced, diversified investment strategy, with the intent of maximizing returns without exposure to undue risk. Investments are typically made through investment managers across several investment categories (domestic large and small cap, international, domestic fixed income, real estate, hedge funds and private equity), with selective exposure to Growth/Value investment styles. Performance for each investment is measured relative to the appropriate index benchmark for its category. Target asset-allocation percentages by major category are 45%-55% equity securities, 20%-30% fixed income and up to 25% in a combination of other investments such as real estate, hedge funds and private equity. Investment managers have full discretion as to investment decisions regarding all funds under their management to the extent permitted within investment guidelines.        Although investment managers may, at their discretion and within investment guidelines, invest in Anadarko securities, there are no material direct investments in Anadarko securities included in plan assets. There may be, however, indirect investments in Anadarko securities through the plans' mutual fund investments. The expected long-term rate of return on plan assets assumption was determined using the year-end 2010 pension investment balances by asset class and expected long-term asset allocation. The expected return for each asset class reflects capital-market projections formulated using a forward-looking building-block approach, while also taking into account historical return trends and current market conditions. Equity returns generally reflect long-term expectations of real earnings growth, dividend yield, and inflation. Returns on fixed-income securities are generally developed based on expected inflation, real bond yield, and risk spread (as appropriate), adjusted for the expected effect that changing yields have on the rate return. Other asset class returns are derived from their relationship to the equity and fixed income markets.Investment Policies and Strategies   The Company has adopted a balanced, diversified investment strategy, with the intent of maximizing returnsfalsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringDefined benefit plan investment policies disclosure.No authoritative reference available.falsefalseDefined Benefit Plan Investment Policies123Summary of Significant Accounting Policies (Policies)UnKnownUnKnownUnKnownUnKnownfalsetrue