Share-Based Compensation (Schedule Of Share-Based Compensation Expense Included In The Consolidated Statements Of Comprehensive Earnings) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expense	$ 88	$ 115	$ 137
Related income tax benefit		13	17
G&A [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expense	76	83	104
Exploration Expenses [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expense	1	1	2
Restructuring and Transaction Costs [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Accelerated share-based compensation expense	$ 11	$ 31	$ 31

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Amount of tax benefit for recognition of expense of award under share-based payment arrangement.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Amount of additional cost recognized for award under share-based payment arrangement from occurrence of event accelerating recognition of cost.

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