Identification of the specific currency to be purchased upon settlement or exercise of the foreign currency derivative.

No definition available.

Name:	us-gaap_DerivativeCurrencyBought
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Identification of the specific currency to be sold upon settlement or exercise of the foreign currency derivative.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeCurrencySold
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Contractual rate at which a foreign currency can be purchased or sold.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeForwardExchangeRate1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Nominal or face amount used to calculate payment on derivative.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579245-113959

+ Details

Name:	us-gaap_DerivativeNotionalAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

General discussion of the entity's activities involving foreign currency derivatives not designated as hedging instruments.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=109980867&loc=d3e41638-113959

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5579240-113959

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109980867&loc=d3e41620-113959

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=109980867&loc=d3e41641-113959

+ Details

Name:	us-gaap_DescriptionOfForeignCurrencyDerivativeInstrumentsNotDesignatedAsHedgingInstrumentsActivities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

Name:	us-gaap_NotionalAmountOfDerivativesAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=cop_BuyBritishPoundSellEuroMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=cop_SellCanadianDollarBuyUSDollarMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_HedgingDesignationAxis=us-gaap_NondesignatedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=cop_BuyCanadianDollarCurrencySellUnitedStatesCurrencyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Derivative and Financial Instruments - FX Notional (Details) £ in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2020 CAD ($) $ / $	Jun. 30, 2019 CAD ($) $ / $	Jun. 30, 2020 CAD ($)	Jun. 30, 2020 GBP (£)	Dec. 31, 2019 CAD ($)	Dec. 31, 2019 GBP (£)
Notional Disclosures [Abstract]
Description of Foreign Currency Derivative Instruments Not Designated as Hedging Instruments Activities			In the second quarter of 2019, we entered into foreign currency exchange contracts to sell CAD 1.35 billion at CAD 0.748 against the USD. In the first quarter of 2020, we entered into forward currency exchange contracts to buy CAD 0.9 billion at CAD 0.718 against the USD
Buy British Pound Sell Euro [Member]
Notional Disclosures [Abstract]
Net notional position of foreign currency exchange derivatives \| £				£ 7		£ 4
Sell Canadian dollar, buy U.S. dollar [Member]
Notional Disclosures [Abstract]
Net notional position of foreign currency exchange derivatives			$ 427		$ 1,337
Sell Canadian dollar, buy U.S. dollar [Member] \| Nondesignated [Member]
Notional Disclosures [Abstract]
Net notional position of foreign currency exchange derivatives		$ 1,350
Derivative, Currency Bought		USD
Derivative, Currency Sold		CAD
Derivative, Forward Exchange Rate \| $ / $		0.748
Buy CAD, Sell USD [Member] \| Nondesignated [Member]
Notional Disclosures [Abstract]
Net notional position of foreign currency exchange derivatives	$ 900
Derivative, Currency Bought	CAD
Derivative, Currency Sold	USD
Derivative, Forward Exchange Rate \| $ / $	0.718