Significant accounting policies (Policies)	6 Months Ended
Jun. 30, 2019
Policy Text Block [Abstract]
Basis of Accounting, Policy [Policy Text Block]	The interim-period financial information presented in the financial statements included in this report is unaudited and, in the opinion of management, includes all known accruals and adjustments necessary for a fair presentation of the consolidated financial position of ConocoPhillips and its results of operations and cash flows for such periods. All such adjustments are of a normal and recurring nature unless otherwise disclosed. Certain notes and other information have been condensed or omitted from the interim financial statements included in this report. Therefore, these financial statements should be read in conjunction with the consolidated financial statements and notes included in our 2018 Annual Report on Form 10-K.
New Accounting Pronouncements, Policy [Policy Text Block]	We adopted the provisions of FASB ASU No. 2016-02, “Leases,” and its amendments set forth by the provisions of ASU No. 2018-01, “Land Easement Practical Expedient for Transition to Topic 842,” ASU No. 2018-10, “Codification Improvements to Topic 842, Leases,” ASU No. 2018-11, “Targeted Improvements,” ASU No. 2018-20, “Narrow-Scope Improvements for Lessors,” and ASU No. 2019-01, “Codification Improvements,” collectively FASB ASC Topic 842, “Leases” (ASC Topic 842), beginning January 1, 2019. ASC Topic 842 establishes comprehensive accounting and financial reporting requirements for leasing arrangements, supersedes the existing requirements in FASB ASC Topic 840, “Leases” (ASC Topic 840), and requires lessees to recognize substantially all lease assets and lease liabilities on the balance sheet. The provisions of ASC Topic 842 also modify the definition of a lease and outline requirements for recognition, measurement, presentation and disclosure of leasing arrangements by both lessees and lessors. We adopted ASC Topic 842 using the modified retrospective approach and elected to utilize the Optional Transition Method, which permits us to apply the provisions of ASC Topic 842 to leasing arrangements existing at or entered into after January 1, 2019, and present in our financial statements comparative periods prior to January 1, 2019 under the historical requirements of ASC Topic 840. In addition, we elected to adopt the package of optional transition-related practical expedients, which among other things, allows us to carry forward certain historical conclusions reached under ASC Topic 840 regarding lease identification, classification, and the accounting treatment of initial direct costs. Furthermore, we elected not to record assets and liabilities on our consolidated balance sheet for new or existing lease arrangements with terms of 12 months or less. The primary impact of applying ASC Topic 842 is the initial recognition of $998 million of lease liabilities and corresponding right-of-use assets on our consolidated balance sheet as of January 1, 2019, for leases classified as operating leases under ASC Topic 840, as well as enhanced disclosure of our leasing arrangements. Our accounting treatment for finance leases remains unchanged. In addition, there is no cumulative effect to retained earnings or other components of equity recognized as of January 1, 2019, and the adoption of ASC Topic 842 did not impact the presentation of our consolidated income statement or statement of cash flows. See Note 15—Non-Mineral Leases for additional information related to the adoption of ASC Topic 842. We adopted the provisions of FASB ASU No. 2018-02, “Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income,” beginning January 1, 2019. The ASU allows a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act, eliminating the stranded tax effects.
Revenue Recognition, Policy [Policy Text Block]	Typically, our commodity sales contracts are less than 12 months in duration; however, in certain specific cases may extend longer, which may be out to the end of field life. We have long-term commodity sales contracts which use prevailing market prices at the time of delivery, and under these contracts, the market-based variable consideration for each performance obligation (i.e., delivery of commodity) is allocated to each wholly unsatisfied performance obligation within the contract. Accordingly, we have applied the practical expedient allowed in ASC Topic 606 and do not disclose the aggregate amount of the transaction price allocated to performance obligations or when we expect to recognize revenues that are unsatisfied (or partially unsatisfied) as of the end of the reporting period.
Long-Duration Contracts Revenue Recognition, Policy [Policy Text Block]	We have entered into contractual arrangements where we license proprietary technology to customers related to the optimization process for operating LNG plants. The agreements typically provide for negotiated payments to be made at stated milestones. The payments are not directly related to our performance under the contract and are recorded as deferred revenue to be recognized as revenue when the customer can utilize and benefit from their right to use the license. Payments are received in installments over the construction period.
Lessee, Leases [Policy Text Block]	We adopted ASC Topic 842 using the modified retrospective approach and elected to utilize the Optional Transition Method, which permits us to apply the provisions of ASC Topic 842 to leasing arrangements existing at or entered into after January 1, 2019, and present in our financial statements comparative periods prior to January 1, 2019 under the historical requirements of ASC Topic 840. In addition, we elected to adopt the package of optional transition-related practical expedients, which among other things, allows us to carry forward certain historical conclusions reached under ASC Topic 840 regarding lease identification, classification, and the accounting treatment of initial direct costs. Furthermore, we elected not to record assets and liabilities on our consolidated balance sheet for new or existing lease arrangements with terms of 12 months or less. The primary impact of applying ASC Topic 842 is the initial recognition of $998 million of lease liabilities and corresponding right-of-use assets on our consolidated balance sheet as of January 1, 2019, for leases classified as operating leases under ASC Topic 840, as well as enhanced disclosure of our leasing arrangements. Our accounting treatment for finance leases remains unchanged. In addition, there is no cumulative effect to retained earnings or other components of equity recognized as of January 1, 2019, and the adoption of ASC Topic 842 did not impact the presentation of our consolidated income statement or statement of cash flows. See Note 15—Non-Mineral Leases for additional information related to the adoption of ASC Topic 842.

Significant accounting policies (Policies)

6 Months Ended

Jun. 30, 2019

Basis of Accounting, Policy [Policy Text Block]

The interim-period financial information presented in the financial statements included in this report is unaudited and, in the opinion of management, includes all known accruals and adjustments necessary for a fair presentation of the consolidated financial position of ConocoPhillips and its results of operations and cash flows for such periods. All such adjustments are of a normal and recurring nature unless otherwise disclosed. Certain notes and other information have been condensed or omitted from the interim financial statements included in this report. Therefore, these financial statements should be read in conjunction with the consolidated financial statements and notes included in our 2018 Annual Report on Form 10-K.

New Accounting Pronouncements, Policy [Policy Text Block]

We adopted the provisions of FASB ASU No. 2016-02, “Leases,” and its amendments set forth by the provisions of ASU No. 2018-01, “Land Easement Practical Expedient for Transition to Topic 842,” ASU No. 2018-10, “Codification Improvements to Topic 842, Leases,” ASU No. 2018-11, “Targeted Improvements,” ASU No. 2018-20, “Narrow-Scope Improvements for Lessors,” and ASU No. 2019-01, “Codification Improvements,” collectively FASB ASC Topic 842, “Leases” (ASC Topic 842), beginning January 1, 2019.

ASC Topic 842 establishes comprehensive accounting and financial reporting requirements for leasing arrangements, supersedes the existing requirements in FASB ASC Topic 840, “Leases” (ASC Topic 840), and requires lessees to recognize substantially all lease assets and lease liabilities on the balance sheet. The provisions of ASC Topic 842 also modify the definition of a lease and outline requirements for recognition, measurement, presentation and disclosure of leasing arrangements by both lessees and lessors.

We adopted ASC Topic 842 using the modified retrospective approach and elected to utilize the Optional Transition Method, which permits us to apply the provisions of ASC Topic 842 to leasing arrangements existing at or entered into after January 1, 2019, and present in our financial statements comparative periods prior to January 1, 2019 under the historical requirements of ASC Topic 840. In addition, we elected to adopt the package of optional transition-related practical expedients, which among other things, allows us to carry forward certain historical conclusions reached under ASC Topic 840 regarding lease identification, classification, and the accounting treatment of initial direct costs. Furthermore, we elected not to record assets and liabilities on our consolidated balance sheet for new or existing lease arrangements with terms of 12 months or less.

The primary impact of applying ASC Topic 842 is the initial recognition of $998 million of lease liabilities and corresponding right-of-use assets on our consolidated balance sheet as of January 1, 2019, for leases classified as operating leases under ASC Topic 840, as well as enhanced disclosure of our leasing arrangements. Our accounting treatment for finance leases remains unchanged. In addition, there is no cumulative effect to retained earnings or other components of equity recognized as of January 1, 2019, and the adoption of ASC Topic 842 did not impact the presentation of our consolidated income statement or statement of cash flows. See Note 15—Non-Mineral Leases for additional information related to the adoption of ASC Topic 842.

We adopted the provisions of FASB ASU No. 2018-02, “Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income,” beginning January 1, 2019. The ASU allows a reclassification from accumulated other comprehensive income to retained earnings for stranded tax effects resulting from the Tax Cuts and Jobs Act, eliminating the stranded tax effects.

Revenue Recognition, Policy [Policy Text Block]

Typically, our commodity sales contracts are less than 12 months in duration; however, in certain specific cases may extend longer, which may be out to the end of field life. We have long-term commodity sales contracts which use prevailing market prices at the time of delivery, and under these contracts, the market-based variable consideration for each performance obligation (i.e., delivery of commodity) is allocated to each wholly unsatisfied performance obligation within the contract. Accordingly, we have applied the practical expedient allowed in ASC Topic 606 and do not disclose the aggregate amount of the transaction price allocated to performance obligations or when we expect to recognize revenues that are unsatisfied (or partially unsatisfied) as of the end of the reporting period.

Long-Duration Contracts Revenue Recognition, Policy [Policy Text Block]

We have entered into contractual arrangements where we license proprietary technology to customers related to the optimization process for operating LNG plants. The agreements typically provide for negotiated payments to be made at stated milestones. The payments are not directly related to our performance under the contract and are recorded as deferred revenue to be recognized as revenue when the customer can utilize and benefit from their right to use the license. Payments are received in installments over the construction period.

Lessee, Leases [Policy Text Block]