Supplemental Oil and Gas Disclosures (Unaudited) (Capitalized Costs Relating to Oil and Gas Producing Activities Disclosure) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Oil and Gas Exploration and Production Industries Disclosures [Abstract]
Proved properties	$ 25,789	$ 23,744
Unproved properties	1,472	1,506
Total capitalized costs	27,261	25,250
Less: Accumulated depreciation, depletion and amortization	(23,362)	(20,203)
Net capitalized costs	$ 3,899	$ 5,047

Amount of accumulated depreciation, depletion, amortization and valuation allowance relating to oil and gas producing activities.

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The sum of capitalized costs relating to oil and gas producing activities before accounting for accumulated depreciation.

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Net amount of capitalized costs relating to oil and gas producing activities.

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Capitalized costs of proved properties incurred for any combination mineral interests acquisitions; wells and related equipment; support equipment and facilities; and uncompleted wells and equipment and other costs not previously disclosed within this table.

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Capitalized costs of unproved properties incurred for any combination mineral interests acquisitions and other costs not previously disclosed within this table.

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