v2.4.0.6

Employee Benefit Plans - Fair Values Of Our Pension Plan Assets (Parenthetical) (Detail) (Level 3 [Member], USD $) In Millions, unless otherwise specified | Dec. 31, 2011 | Dec. 31, 2010
--- | --- | ---
Level 3 [Member] |  |
Pension Plans, Postretirement and Other Employee Benefits [Line Items] |  |
Fair value of participating interest in debt security | $ 144 | $ 92
Net receivables related to security transactions | $ 19 | $ 15

X
- Definition Fair value of participating interest in annuity contract. + References No definition available. + Details
Name: | cop_FairValueOfParticipatingInterestInAnnuityContract
Namespace Prefix: | cop_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

X
- Definition Receivables related to security transactions. + References No definition available. + Details
Name: | cop_ReceivablesRelatedToSecurityTransactions
Namespace Prefix: | cop_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant