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Proved oil reserves are the estimated quantities of crude oil and natural gas liquids which geological and engineering data demonstrate with reasonable certainty to be recoverable.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 19 -Paragraph 59F Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 10 -Paragraph a -Subparagraph 2 -Article 4 falsefalseProved reserves, ending balance67false0us-gaap_ProvedDevelopedReservesVolumeus-gaaptruenainstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse150150falsefalsefalsefalsefalse2truefalsefalse144144falsefalsefalsefalsefalse3truefalsefalse145145falsefalsefalsefalsefalse4truefalsefalse182182falsefalsefalsefalsefalseOtherus-types:volumeItemTypedecimalNet quantities of an enterprise's interests in proved developed reserves of either crude oil (including condensate and natural gas liquids) or natural gas as of the beginning and the end of the year. 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The unit of measure for reserve quantities should be defined in the unit attribute of the instance document as "barrels" for oil reserves or "cubic_feet" or "cubic_meters" for natural gas reserves.No authoritative reference available.falsefalseProved Undeveloped Reserves84false0natruenanaNo definition available.falsetruefalsefalsefalsefalsefalsefalsefalsefalsehttp://www.anadarko.com/role/disclosureoilandgasreservestabledetail1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalse37falsefalsetruefalse{us-gaap_ReserveQuantitiesByTypeOfReserveAxis} : Oil Reserves [Member] 1/1/2010 - 12/31/2010 FROM_Jan01_2010_TO_Dec31_2010_us-gaap_ReserveQuantitiesByTypeOfReserveAxis_OilReservesMemberhttp://www.sec.gov/CIK0000773910duration2010-01-01T00:00:002010-12-31T00:00:00falsefalseOil Reserves [Member]us-gaap_ReserveQuantitiesByTypeOfReserveAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_OilReservesMemberus-gaap_ReserveQuantitiesByTypeOfReserveAxisexplicitMemberMMBblsStandardhttp://www.anadarko.com/20101231MMBblsapc038falsefalsetruefalse{us-gaap_ReserveQuantitiesByTypeOfReserveAxis} : Oil Reserves [Member] 1/1/2009 - 12/31/2009 FROM_Jan01_2009_TO_Dec31_2009_us-gaap_ReserveQuantitiesByTypeOfReserveAxis_OilReservesMemberhttp://www.sec.gov/CIK0000773910duration2009-01-01T00:00:002009-12-31T00:00:00falsefalseOil Reserves [Member]us-gaap_ReserveQuantitiesByTypeOfReserveAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_OilReservesMemberus-gaap_ReserveQuantitiesByTypeOfReserveAxisexplicitMemberMMBblsStandardhttp://www.anadarko.com/20101231MMBblsapc039falsefalsetruefalse{us-gaap_ReserveQuantitiesByTypeOfReserveAxis} : Oil Reserves [Member] 1/1/2008 - 12/31/2008 FROM_Jan01_2008_TO_Dec31_2008_us-gaap_ReserveQuantitiesByTypeOfReserveAxis_OilReservesMemberhttp://www.sec.gov/CIK0000773910duration2008-01-01T00:00:002008-12-31T00:00:00falsefalseOil Reserves [Member]us-gaap_ReserveQuantitiesByTypeOfReserveAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_OilReservesMemberus-gaap_ReserveQuantitiesByTypeOfReserveAxisexplicitMemberMMBblsStandardhttp://www.anadarko.com/20101231MMBblsapc040falsefalsetruefalse{us-gaap_ReserveQuantitiesByTypeOfReserveAxis} : Oil Reserves [Member] 1/1/2007 - 12/31/2007 FROM_Jan01_2007_TO_Dec31_2007_us-gaap_ReserveQuantitiesByTypeOfReserveAxis_OilReservesMemberhttp://www.sec.gov/CIK0000773910duration2007-01-01T00:00:002007-12-31T00:00:00falsefalseOil Reserves [Member]us-gaap_ReserveQuantitiesByTypeOfReserveAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_OilReservesMemberus-gaap_ReserveQuantitiesByTypeOfReserveAxisexplicitMemberMMBblsStandardhttp://www.anadarko.com/20101231MMBblsapc0OthernaNo definition available.No authoritative reference available.falsefalseOil Reserves [Member]85false0us-gaap_ProvedDevelopedAndUndevelopedReservesNetus-gaaptruenainstantNo definition available.falsefalsefalsefalsefalsefalsefalsetruefalsefalseperiodstartlabel1truefalsefalse733733falsefalsefalsefalsefalse2truefalsefalse709709falsefalsefalsefalsefalse3truefalsefalse843843falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:decimalItemTypedecimalThe net quantity of proved oil reserves as of the balance sheet date. Proved oil reserves are the estimated quantities of crude oil and natural gas liquids which geological and engineering data demonstrate with reasonable certainty to be recoverable.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 19 -Paragraph 59F Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 10 -Paragraph a -Subparagraph 2 -Article 4 falsefalseProved reserves, beginning balance86false0us-gaap_ProvedDevelopedAndUndevelopedReservesRevisionsOfPreviousEstimatesIncreaseDecreaseus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse7676falsefalsefalsefalsefalse2truefalsefalse6161falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:decimalItemTypedecimalRevisions represent changes in previous estimates of proved oil reserves, either upward or downward, resulting from new information (except for an increase in proved acreage) normally obtained from development drilling and production history or resulting from change in economic factors.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 19 -Paragraph 59F -Subparagraph a falsefalseRevisions of prior estimates87false0us-gaap_ProvedDevelopedAndUndevelopedReservesExtensionsDiscoveriesAndAdditionsus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse1313falsefalsefalsefalsefalse2truefalsefalse3333falsefalsefalsefalsefalse3truefalsefalse3636falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:decimalItemTypedecimalAdditions to proved oil reserves that result from (1) extension of the proved acreage of previously discovered (old) reservoirs through additional drilling in periods after discovery and (2) discovery of new fields with proved oil reserves or of new reservoirs of proved oil reserves in old fields.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 19 -Paragraph 59F -Subparagraph d falsefalseExtensions, discoveries and other additions88false0us-gaap_ProvedDevelopedAndUndevelopedReservesPurchasesOfMineralsInPlaceus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00falsefalsefalsefalsefalse2truefalsefalse11falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:decimalItemTypedecimalPurchase of proved oil reserves.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 19 -Paragraph 59F -Subparagraph c falsefalsePurchases in place89false0us-gaap_ProvedDevelopedAndUndevelopedReservesSalesOfMineralsInPlaceus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsetruenegated1falsefalsefalse00falsefalsefalsefalsefalse2truefalsefalse-2-2falsefalsefalsefalsefalse3truefalsefalse-104-104falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:decimalItemTypedecimalSales of proved oil reservesReference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 19 -Paragraph 59F -Subparagraph f falsefalseSales in place90false0us-gaap_ProvedDevelopedAndUndevelopedReservesProductionus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsetruenegated1truefalsefalse-73-73falsefalsefalsefalsefalse2truefalsefalse-69-69falsefalsefalsefalsefalse3truefalsefalse-66-66falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:decimalItemTypedecimalProduction of proved oil reservesReference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 19 -Paragraph 59F -Subparagraph e falsefalseProduction91false0us-gaap_ProvedDevelopedAndUndevelopedReservesNetus-gaaptruenainstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsetruefalseperiodendlabel1truefalsefalse749749falsefalsefalsefalsefalse2truefalsefalse733733falsefalsefalsefalsefalse3truefalsefalse709709falsefalsefalsefalsefalse4truefalsefalse843843falsefalsefalsefalsefalseOtherxbrli:decimalItemTypedecimalThe net quantity of proved oil reserves as of the balance sheet date. Proved oil reserves are the estimated quantities of crude oil and natural gas liquids which geological and engineering data demonstrate with reasonable certainty to be recoverable.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 19 -Paragraph 59F Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 10 -Paragraph a -Subparagraph 2 -Article 4 falsefalseProved reserves, ending balance92false0us-gaap_ProvedDevelopedReservesVolumeus-gaaptruenainstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse453453falsefalsefalsefalsefalse2truefalsefalse444444falsefalsefalsefalsefalse3truefalsefalse430430falsefalsefalsefalsefalse4truefalsefalse449449falsefalsefalsefalsefalseOtherus-types:volumeItemTypedecimalNet quantities of an enterprise's interests in proved developed reserves of either crude oil (including condensate and natural gas liquids) or natural gas as of the beginning and the end of the year. "Net" quantities of reserves include those relating to the enterprise's operating and nonoperating interests in properties. Quantities of reserves relating to royalty interests owned shall be included in "net" quantities if the necessary information is available to the enterprise. "Net" quantities shall not include reserves relating to interests of others in properties owned by the enterprise. The unit of measure for reserve quantities should be defined in the unit attribute of the instance document as "barrels" for oil reserves or "cubic_feet" or "cubic_meters" for natural gas reserves.No authoritative reference available.falsefalseProved Developed Reserves93false0us-gaap_ProvedUndevelopedReservesVolumeus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse296296falsefalsefalsefalsefalse2truefalsefalse289289falsefalsefalsefalsefalse3truefalsefalse279279falsefalsefalsefalsefalse4truefalsefalse394394falsefalsefalsefalsefalseOtherus-types:volumeItemTypedecimalNet quantities of an enterprise's interests in proved undeveloped reserves of either crude oil (including condensate and natural gas liquids) or natural gas as of the beginning and the end of the year. "Net" quantities of reserves include those relating to the enterprise's operating and nonoperating interests in properties. Quantities of reserves relating to royalty interests owned shall be included in "net" quantities if the necessary information is available to the enterprise. "Net" quantities shall not include reserves relating to interests of others in properties owned by the enterprise. 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Proved oil reserves are the estimated quantities of crude oil and natural gas liquids which geological and engineering data demonstrate with reasonable certainty to be recoverable.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 19 -Paragraph 59F Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 10 -Paragraph a -Subparagraph 2 -Article 4 falsefalseProved reserves, beginning balance96false0us-gaap_ProvedDevelopedAndUndevelopedReservesRevisionsOfPreviousEstimatesIncreaseDecreaseus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse5656falsefalsefalsefalsefalse2truefalsefalse7474falsefalsefalsefalsefalse3truefalsefalse5858falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:decimalItemTypedecimalRevisions represent changes in previous estimates of proved oil reserves, either upward or downward, resulting from new information (except for an increase in proved acreage) normally obtained from development drilling and production history or resulting from change in economic factors.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 19 -Paragraph 59F -Subparagraph a falsefalseRevisions of prior estimates97false0us-gaap_ProvedDevelopedAndUndevelopedReservesExtensionsDiscoveriesAndAdditionsus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse1010falsefalsefalsefalsefalse2truefalsefalse22falsefalsefalsefalsefalse3truefalsefalse44falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:decimalItemTypedecimalAdditions to proved oil reserves that result from (1) extension of the proved acreage of previously discovered (old) reservoirs through additional drilling in periods after discovery and (2) discovery of new fields with proved oil reserves or of new reservoirs of proved oil reserves in old fields.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 19 -Paragraph 59F -Subparagraph d falsefalseExtensions, discoveries and other additions98false0us-gaap_ProvedDevelopedAndUndevelopedReservesPurchasesOfMineralsInPlaceus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00falsefalsefalsefalsefalse2truefalsefalse66falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:decimalItemTypedecimalPurchase of proved oil reserves.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 19 -Paragraph 59F -Subparagraph c falsefalsePurchases in place99false0us-gaap_ProvedDevelopedAndUndevelopedReservesSalesOfMineralsInPlaceus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsetruenegated1falsefalsefalse00falsefalsefalsefalsefalse2truefalsefalse-3-3falsefalsefalsefalsefalse3truefalsefalse-2-2falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:decimalItemTypedecimalSales of proved oil reservesReference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 19 -Paragraph 59F -Subparagraph f falsefalseSales in place100false0us-gaap_ProvedDevelopedAndUndevelopedReservesProductionus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsetruenegated1truefalsefalse-23-23falsefalsefalsefalsefalse2truefalsefalse-19-19falsefalsefalsefalsefalse3truefalsefalse-14-14falsefalsefalsefalsefalse4falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:decimalItemTypedecimalProduction of proved oil reservesReference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 19 -Paragraph 59F -Subparagraph e falsefalseProduction101false0us-gaap_ProvedDevelopedAndUndevelopedReservesNetus-gaaptruenainstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsetruefalseperiodendlabel1truefalsefalse320320falsefalsefalsefalsefalse2truefalsefalse277277falsefalsefalsefalsefalse3truefalsefalse217217falsefalsefalsefalsefalse4truefalsefalse171171falsefalsefalsefalsefalseOtherxbrli:decimalItemTypedecimalThe net quantity of proved oil reserves as of the balance sheet date. Proved oil reserves are the estimated quantities of crude oil and natural gas liquids which geological and engineering data demonstrate with reasonable certainty to be recoverable.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 19 -Paragraph 59F Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 10 -Paragraph a -Subparagraph 2 -Article 4 falsefalseProved reserves, ending balance102false0us-gaap_ProvedDevelopedReservesVolumeus-gaaptruenainstantNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse222222falsefalsefalsefalsefalse2truefalsefalse199199falsefalsefalsefalsefalse3truefalsefalse150150falsefalsefalsefalsefalse4truefalsefalse125125falsefalsefalsefalsefalseOtherus-types:volumeItemTypedecimalNet quantities of an enterprise's interests in proved developed reserves of either crude oil (including condensate and natural gas liquids) or natural gas as of the beginning and the end of the year. "Net" quantities of reserves include those relating to the enterprise's operating and nonoperating interests in properties. Quantities of reserves relating to royalty interests owned shall be included in "net" quantities if the necessary information is available to the enterprise. "Net" quantities shall not include reserves relating to interests of others in properties owned by the enterprise. The unit of measure for reserve quantities should be defined in the unit attribute of the instance document as "barrels" for oil reserves or "cubic_feet" or "cubic_meters" for natural gas reserves.No authoritative reference available.falsefalseProved Developed Reserves103false0us-gaap_ProvedUndevelopedReservesVolumeus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse9898falsefalsefalsefalsefalse2truefalsefalse7878falsefalsefalsefalsefalse3truefalsefalse6767falsefalsefalsefalsefalse4truefalsefalse4646falsefalsefalsefalsefalseOtherus-types:volumeItemTypedecimalNet quantities of an enterprise's interests in proved undeveloped reserves of either crude oil (including condensate and natural gas liquids) or natural gas as of the beginning and the end of the year. "Net" quantities of reserves include those relating to the enterprise's operating and nonoperating interests in properties. Quantities of reserves relating to royalty interests owned shall be included in "net" quantities if the necessary information is available to the enterprise. "Net" quantities shall not include reserves relating to interests of others in properties owned by the enterprise. The unit of measure for reserve quantities should be defined in the unit attribute of the instance document as "barrels" for oil reserves or "cubic_feet" or "cubic_meters" for natural gas reserves.No authoritative reference available.falsefalseProved Undeveloped Reserves1Revisions of prior estimates for 2010, 2009 and 2008 total reserves include 312 MMBOE, 125 MMBOE and 158 MMBOE, respectively, of additions generated by Anadarko’s infill drilling programs.4102Oil and Gas Reserves Table (Detail)UnKnownUnKnownUnKnownUnKnowntruetrue