Joint Venture Acquisition Obligation (Details) (USD $)	3 Months Ended
Mar. 31, 2013
Joint Venture Acquisition Obligation (Textual) [Abstract]
Initial acquisition obligation to joint venture	$ 7,500,000,000
Time period for contribution	10
Quarterly principal and interest payments for joint venture acquisition obligation	237,000,000
Short-term portion of principal obligation amount	782,000,000
Principal payment for joint venture obligation	$ 189,000,000
Fixed-rate on joint venture acquisition obligation	5.30%
Percentage of quarterly interest payment as capital contribution	50.00%

Fixed annual interest rate on joint venture acquisition obligation.

No definition available.

Name:	cop_FixedAnnualInterestRateOnJointVentureAcquisitionObligation
Namespace Prefix:	cop_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Obligation to Joint Venture over a 10-year period, beginning in 2007.

No definition available.

Name:	cop_InitialAcquisitionObligationToJointVenture
Namespace Prefix:	cop_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of the required quarterly payments applied to principal.

No definition available.

Name:	cop_JointVentureAcquisitionObligationPrincipalPayment
Namespace Prefix:	cop_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Amount of the required quarterly payments including both interest and principal payments for Joint Venture Acquisition Obligation.

No definition available.

Name:	cop_JointVentureAcquisitionObligationQuarterlyPayment
Namespace Prefix:	cop_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Name:	cop_JointVentureAcquisitionObligationTextualAbstract
Namespace Prefix:	cop_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Percent of the quarterly interest payment that is reflected as a capital contribution.

No definition available.

Name:	cop_PercentOfQuarterlyInterestPaymentAsCapitalContribution
Namespace Prefix:	cop_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Short-term portion of principal obligation amount.

No definition available.

Name:	cop_ShortTermPortionOfPrincipalObligationAmount
Namespace Prefix:	cop_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Time period for contribution.

No definition available.

Name:	cop_TimePeriodForContribution
Namespace Prefix:	cop_
Data Type:	us-types:durationStringItemType
Balance Type:	na
Period Type:	duration