Assets Acquisitions and Dispositions Textuals (Details) shares in Millions			1 Months Ended								3 Months Ended						12 Months Ended
	Jan. 15, 2021 USD ($) shares	May 27, 2020 USD ($) MBoe	Aug. 31, 2020 USD ($) a	May 31, 2020 USD ($)	Mar. 31, 2020 USD ($)	Feb. 29, 2020 USD ($)	Sep. 30, 2019 USD ($)	Apr. 30, 2019 USD ($)	Jan. 31, 2019 USD ($)	Oct. 31, 2018 USD ($)	Dec. 31, 2019 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Jan. 31, 2021 USD ($)	Dec. 18, 2018 USD ($)	May 17, 2017
Income related items for assets held for sale [Abstract]
Income (Loss) From Equity Method Investments																	$ 432,000,000	$ 779,000,000	$ 1,074,000,000
Exploration Expense																	1,457,000,000	743,000,000	369,000,000
Gain (Loss) on Disposition of Oil and Gas Property [Abstract]
Equity Method Investments											$ 8,234,000,000						7,596,000,000	8,234,000,000
Business Combinations [Abstract]
Business Combination, Consideration Transferred	$ 13,100,000,000
Business Combination, Share Exchange Ratio	1.46
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt	$ 3,900,000,000
Concho Resources Inc [Member] | Subsequent Event [Member]
Business Combinations [Abstract]
Business Combination, Consideration Transferred	$ 13,125,000,000
Business Combination, Share Exchange Ratio	1.46
Business Combination, Consideration Transferred, Equity Interests Issued and Issuable, Shares | shares	286
Long-term Debt	$ 3,900,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt	$ 4,700,000,000
Operating Segments [Member]
Income related items for assets held for sale [Abstract]
Income (Loss) From Equity Method Investments																	432,000,000	779,000,000	1,074,000,000
Corporate, Non-Segment [Member]
Income related items for assets held for sale [Abstract]
Income (Loss) From Equity Method Investments																	0	0	0
Alaska Segment [Member] | Operating Segments [Member]
Income related items for assets held for sale [Abstract]
Income (Loss) From Equity Method Investments																	(7,000,000)	7,000,000	6,000,000
Lower 48 Segment [Member]
Income related items for assets held for sale [Abstract]
Exploration Expense																		141,000,000
Lower 48 Segment [Member] | Operating Segments [Member]
Income related items for assets held for sale [Abstract]
Income (Loss) From Equity Method Investments																	(11,000,000)	(159,000,000)	1,000,000
Canada Segment [Member] | Operating Segments [Member]
Income related items for assets held for sale [Abstract]
Income (Loss) From Equity Method Investments																	0	0	0
Canada Segment [Member] | Operating Segments [Member] | Montney [Member]
Business Combinations [Abstract]
Oil and Gas, Undeveloped Acreage, Net | a			295,000
Noncontrolling Interest, Ownership Percentage by Parent			100.00%
Canada Segment [Member] | Operating Segments [Member] | Additional Montney Acreage [Member]
Business Combinations [Abstract]
Payments To Acquire Businesses, Gross			$ 382,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Financial Liabilities																				$ 31,000,000
Oil and Gas, Undeveloped Acreage, Net | a			140,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment			$ 490,000,000
Asset retirement obligations and accrued environmental costs			77,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt			$ 31,000,000
Asia Pacific and Middle East Segment [Member] | Operating Segments [Member]
Income related items for assets held for sale [Abstract]
Income (Loss) From Equity Method Investments																	137,000,000	461,000,000	323,000,000
Asia Pacific [Member]
Income related items for assets held for sale [Abstract]
Exploration Expense																	50,000,000
Europe and North Africa Segment [Member] | Operating Segments [Member]
Income related items for assets held for sale [Abstract]
Income (Loss) From Equity Method Investments																	311,000,000	470,000,000	744,000,000
Australia West Assets [Member] | Asia Pacific [Member] | Operating Segments [Member]
Asset Held For Sale Transaction Detail [Abstract]
Proceeds from asset dispositions				$ 765,000,000
Disposal Group, Including Discontinued Operation, Assets, Current [Abstract]
Net carrying value		$ 200,000,000
Disposition, Cash		500,000,000
Disposition, PP&E		1,300,000,000
Disposition, Other current assets		100,000,000
Asset Retirement Obligation of held for sale or sold		700,000,000
Disposition, deferred tax liabilities		300,000,000
Disposition, other liabilities		$ 200,000,000
Disposition, Before-tax earnings																	(851,000,000)	(372,000,000)	(364,000,000)
Gain (Loss) on Disposition of Oil and Gas Property [Abstract]
Before-tax gain (loss) on disposition																	$ 587,000,000
Barossa project [Member] | Asia Pacific [Member] | Operating Segments [Member]
Gain (Loss) on Disposition of Oil and Gas Property [Abstract]
Production | MBoe		43
Barossa project [Member] | Asia Pacific [Member] | Operating Segments [Member] | Scenario Plan [Member]
Asset Held For Sale Transaction Detail [Abstract]
Proceeds from asset dispositions				$ 200,000,000
Caldita Field [Member] | Asia Pacific and Middle East Segment [Member] | Operating Segments [Member]
Asset Held For Sale Transaction Detail [Abstract]
Ownership Percent																	37.50%
Bayu-Undan Field [Member] | Asia Pacific and Middle East Segment [Member] | Operating Segments [Member]
Asset Held For Sale Transaction Detail [Abstract]
Ownership Percent																	56.90%
Niobrara [Member] | Lower 48 Segment [Member]
Asset Held For Sale Transaction Detail [Abstract]
Proceeds from asset dispositions					$ 359,000,000
Disposal Group, Including Discontinued Operation, Assets, Current [Abstract]
Net carrying value					397,000,000
Disposition, PP&E					433,000,000
Asset Retirement Obligation of held for sale or sold					34,000,000
Gain (Loss) on Disposition of Oil and Gas Property [Abstract]
Before-tax gain (loss) on disposition					$ 38,000,000
Niobrara [Member] | Lower 48 Segment [Member] | Operating Segments [Member]
Income related items for assets held for sale [Abstract]
Results Of Operations Income Before Income Taxes																	$ 25,000,000	372,000,000	35,000,000
Impairment of asset held for sale											386,000,000
Golden Pass [Member] | Lower 48 Segment [Member] | Operating Segments [Member]
Asset Held For Sale Transaction Detail [Abstract]
Ownership percentage in equity investment									12.40%
Income related items for assets held for sale [Abstract]
Income (Loss) From Equity Method Investments									$ 60,000,000
U.K. Subsidiaries [Member] | Operating Segments [Member]
Gain (Loss) on Disposition of Oil and Gas Property [Abstract]
After-tax gain (loss) on disposition											2,100,000		$ 900,000					2,100,000	900,000
U.K. Subsidiaries [Member] | Europe and North Africa Segment [Member] | Operating Segments [Member] | Scenario Plan [Member]
Asset Held For Sale Transaction Detail [Abstract]
Proceeds from asset dispositions							$ 2,200,000,000	$ 2,675,000,000
Disposal Group, Including Discontinued Operation, Assets, Current [Abstract]
Net carrying value							500,000,000
Disposition, PP&E							1,600,000,000
Working Capital and cash in net carrying value							100,000,000
Amount of deferred taxes in carrying value of asset							300,000,000
Cumulative foreign currency translation adjustments							500,000,000
Gain (Loss) on Disposition of Oil and Gas Property [Abstract]
Before-tax gain (loss) on disposition																		1,700,000,000
After-tax gain (loss) on disposition											2,100,000,000							2,100,000,000
U.K. Subsidiaries [Member] | Europe and North Africa Segment [Member] | Operating Segments [Member] | Asset Retirement Obligation Costs [Member]
Disposal Group, Including Discontinued Operation, Assets, Current [Abstract]
Asset Retirement Obligation of held for sale or sold							$ 1,800,000,000
Greater Sunrise Fields [Member] | Asia Pacific and Middle East Segment [Member] | Operating Segments [Member]
Asset Held For Sale Transaction Detail [Abstract]
Proceeds from asset dispositions												$ 350,000,000
Ownership Percent												30.00%
Gain (Loss) on Disposition of Oil and Gas Property [Abstract]
After-tax gain (loss) on disposition												$ 52,000,000
Magnolia Field And Platform [Member] | Lower 48 Segment [Member] | Operating Segments [Member]
Asset Held For Sale Transaction Detail [Abstract]
Proceeds from asset dispositions											16,000,000
Disposal Group, Including Discontinued Operation, Assets, Current [Abstract]
Disposition, PP&E											4,000,000							4,000,000
Gain (Loss) on Disposition of Oil and Gas Property [Abstract]
Before-tax gain (loss) on disposition											82,000,000
Magnolia Field And Platform [Member] | Lower 48 Segment [Member] | Operating Segments [Member] | Asset Retirement Obligation Costs [Member]
Disposal Group, Including Discontinued Operation, Assets, Current [Abstract]
Asset retirement obligation at disposal											$ 70,000,000							$ 70,000,000
Other properties [Member] | Lower 48 Segment [Member] | Operating Segments [Member]
Asset Held For Sale Transaction Detail [Abstract]
Proceeds from asset dispositions																$ 112,000,000
Gain (Loss) on Disposition of Oil and Gas Property [Abstract]
Before-tax gain (loss) on disposition																$ 0
Undeveloped Leasehold Assets [Member] | Lower 48 Segment [Member] | Operating Segments [Member]
Asset Held For Sale Transaction Detail [Abstract]
Proceeds from asset dispositions													162,000,000	$ 56,000,000	$ 105,000,000
Gain (Loss) on Disposition of Oil and Gas Property [Abstract]
Before-tax gain (loss) on disposition													140,000,000		$ 0
Barnett [Member] | Lower 48 Segment [Member] | Operating Segments [Member]
Asset Held For Sale Transaction Detail [Abstract]
Proceeds from asset dispositions										$ 196,000,000
Disposal Group, Including Discontinued Operation, Assets, Current [Abstract]
Net carrying value										201,000,000
Disposition, PP&E										250,000,000
Gain (Loss) on Disposition of Oil and Gas Property [Abstract]
Before-tax gain (loss) on disposition										5,000,000
Barnett [Member] | Lower 48 Segment [Member] | Operating Segments [Member] | Asset Retirement Obligation Costs [Member]
Disposal Group, Including Discontinued Operation, Assets, Current [Abstract]
Asset retirement obligation at disposal										$ 49,000,000
Income related items for assets held for sale [Abstract]
Results Of Operations Income Before Income Taxes																			(59,000,000)
U.K. subsidiary holding Clair field | Europe and North Africa Segment [Member] | Operating Segments [Member]
Asset Held For Sale Transaction Detail [Abstract]
Proceeds from asset dispositions													253,000,000
Ownership Percent																					16.50%
Ownership percentage retained																					7.50%
Ownership percentage in equity investment																					24.00%
Fair Value Assets Disposed Of																					$ 1,743,000,000
Disposal Group, Including Discontinued Operation, Assets, Current [Abstract]
Net carrying value																					1,028,000,000
Disposition, PP&E																					1,553,000,000
Disposition, deferred tax liabilities																					485,000,000
Income related items for assets held for sale [Abstract]
Results Of Operations Income Before Income Taxes																			$ 748,000,000
Gain (Loss) on Disposition of Oil and Gas Property [Abstract]
Before-tax gain (loss) on disposition													$ 715,000,000
U.K. subsidiary holding Clair field | Europe and North Africa Segment [Member] | Operating Segments [Member] | Asset Retirement Obligation Costs [Member]
Disposal Group, Including Discontinued Operation, Assets, Current [Abstract]
Asset retirement obligation at disposal																					$ 59,000,000
Clair Field [Member] | Europe and North Africa Segment [Member] | Operating Segments [Member]
Asset Held For Sale Transaction Detail [Abstract]
Ownership Percent																					24.00%
Greater Kuparuk Area [Member] | Alaska Segment [Member] | Operating Segments [Member]
Asset Held For Sale Transaction Detail [Abstract]
Ownership Percent																					39.20%
Ownership percentage retained																					38.00%
Foster Creek Christina Lake (FCCL) [Member]
Asset Held For Sale Transaction Detail [Abstract]
Ownership percentage in equity investment																						50.00%
Waddell Ranch [Member] | Lower 48 Segment [Member]
Asset Held For Sale Transaction Detail [Abstract]
Proceeds from asset dispositions						$ 184,000,000
Gain (Loss) on Disposition of Oil and Gas Property [Abstract]
Before-tax gain (loss) on disposition						$ 0