Summary of Significant Accounting Policies	9 Months Ended
Sep. 30, 2011
Disclosure Text Block [Abstract]
Summary of Significant Accounting Policies	1. Summary of Significant Accounting Policies General Anadarko Petroleum Corporation is engaged in the exploration, development, production, and marketing of natural gas, crude oil, condensate, and natural gas liquids (NGLs). In addition, the Company engages in the gathering, processing, and treating of natural gas, and the transporting of 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. Unless the context otherwise requires, the terms “Anadarko” and “Company” refer to Anadarko Petroleum Corporation and its consolidated subsidiaries. Basis of Presentation The information furnished herein reflects all normal recurring adjustments that are, in the opinion of management, necessary for the fair presentation of the Company's Consolidated Balance Sheets as of September 30, 2011, and December 31, 2010, the Consolidated Statements of Income and Comprehensive Income for the three and nine months ended September 30, 2011 and 2010, the Consolidated Statements of Cash Flows for the nine months ended September 30, 2011 and 2010, and the Consolidated Statement of Equity for the nine months ended September 30, 2011. Certain prior-period amounts have been reclassified to conform to the current-period presentation. 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, liabilities, revenues, and expenses. 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, 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. Recently Issued Accounting Standards Not Yet Adopted The Financial Accounting Standards Board (FASB) issued an Accounting Standards Update (ASU) that further addresses fair-value-measurement accounting and related disclosure requirements. The ASU clarifies the FASB's intent regarding the application of existing fair-value-measurement accounting and disclosure requirements, changes fair-value-measurement requirements for certain financial instruments, and sets forth additional disclosure requirements for other fair-value measurements. The ASU is required to be adopted on a prospective basis by Anadarko beginning January 1, 2012. The Company does not expect adoption of this ASU to have an impact on its consolidated financial statements, other than requiring revised disclosures, where appropriate. In September 2011, the FASB issued an ASU that permits an initial assessment of qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount for goodwill impairment testing purposes. Thus, determining a reporting unit's fair value is not required unless, as a result of a qualitative assessment, it is more likely than not that the fair value of the reporting unit is less than its carrying amount. This ASU is effective for periods beginning after December 15, 2011. Adoption of this ASU will have no impact on the Company's consolidated financial statements.

Summary of Significant Accounting Policies

9 Months Ended

Sep. 30, 2011

Summary of Significant Accounting Policies

1. Summary of Significant Accounting Policies

General Anadarko Petroleum Corporation is engaged in the exploration, development, production, and marketing of natural gas, crude oil, condensate, and natural gas liquids (NGLs). In addition, the Company engages in the gathering, processing, and treating of natural gas, and the transporting of 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. Unless the context otherwise requires, the terms “Anadarko” and “Company” refer to Anadarko Petroleum Corporation and its consolidated subsidiaries.

Basis of Presentation The information furnished herein reflects all normal recurring adjustments that are, in the opinion of management, necessary for the fair presentation of the Company's Consolidated Balance Sheets as of September 30, 2011, and December 31, 2010, the Consolidated Statements of Income and Comprehensive Income for the three and nine months ended September 30, 2011 and 2010, the Consolidated Statements of Cash Flows for the nine months ended September 30, 2011 and 2010, and the Consolidated Statement of Equity for the nine months ended September 30, 2011. Certain prior-period amounts have been reclassified to conform to the current-period presentation.

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, liabilities, revenues, and expenses. 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, 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.

Recently Issued Accounting Standards Not Yet Adopted The Financial Accounting Standards Board (FASB) issued an Accounting Standards Update (ASU) that further addresses fair-value-measurement accounting and related disclosure requirements. The ASU clarifies the FASB's intent regarding the application of existing fair-value-measurement accounting and disclosure requirements, changes fair-value-measurement requirements for certain financial instruments, and sets forth additional disclosure requirements for other fair-value measurements. The ASU is required to be adopted on a prospective basis by Anadarko beginning January 1, 2012. The Company does not expect adoption of this ASU to have an impact on its consolidated financial statements, other than requiring revised disclosures, where appropriate.

In September 2011, the FASB issued an ASU that permits an initial assessment of qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount for goodwill impairment testing purposes. Thus, determining a reporting unit's fair value is not required unless, as a result of a qualitative assessment, it is more likely than not that the fair value of the reporting unit is less than its carrying amount. This ASU is effective for periods beginning after December 15, 2011. Adoption of this ASU will have no impact on the Company's consolidated financial statements.