v2.4.0.6

Suspended Wells - Summary of Aging of Suspended Well Costs (Detail) (USD $) In Millions, unless otherwise specified | Dec. 31, 2011 Project | Dec. 31, 2010 Project | Dec. 31, 2009 Project | Dec. 31, 2008
--- | --- | --- | --- | ---
Aging Of Capitalized Exploratory Well Costs [Line Items] |  |  |  |
Exploratory well costs capitalized for a period of one year or less | $ 115 | $ 220 | $ 319 |
Exploratory well costs capitalized for a period greater than one year | 922 | 793 | 589 |
Ending balance | $ 1,037 | $ 1,013 | $ 908 | $ 660
Number of projects that have exploratory well costs that have been capitalized for a period greater than one year | 40 | 40 | 34 |

X
- Details
Name: | cop_AgingOfCapitalizedExploratoryWellCostsLineItems
Namespace Prefix: | cop_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount of capitalized exploratory well costs that is pending the determination of proved reserves. This does not include amounts that were capitalized and subsequently expensed in the same annual period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 1B -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=8451039&loc=SL6806780-109447 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Staff Position (FSP) -Number FAS19-1 -Paragraph 10 -Subparagraph a -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. + Details
Name: | us-gaap_CapitalizedExploratoryWellCosts
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The amount of exploratory well costs that have been capitalized for a period of greater than one year after the completion of drilling. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 1B -Subparagraph b -URI http://asc.fasb.org/extlink&oid=8451039&loc=SL6806780-109447 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Staff Position (FSP) -Number FAS19-1 -Paragraph 10 -Subparagraph b -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. + Details
Name: | us-gaap_CapitalizedExploratoryWellCostsThatHaveBeenCapitalizedForPeriodGreaterThanOneYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The amount of exploratory well costs that have been capitalized for a period of one year or less after the completion of drilling. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Staff Position (FSP) -Number FAS19-1 -Paragraph 10 -Subparagraph b -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 16 -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e61939-109447 + Details
Name: | us-gaap_CapitalizedExploratoryWellCostsThatHaveBeenCapitalizedForPeriodOfOneYearOrLess
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The number of projects for which exploratory well costs have been capitalized for a period of greater than one year after the completion of drilling. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 1B -Subparagraph b -URI http://asc.fasb.org/extlink&oid=8451039&loc=SL6806780-109447 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Staff Position (FSP) -Number FAS19-1 -Paragraph 10 -Subparagraph b -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. + Details
Name: | us-gaap_ProjectsThatHaveExploratoryWellCostsThatHaveBeenCapitalizedForPeriodGreaterThanOneYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant