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Asset Acquisitions and Dispositions - Assets Sold - Textual (Details) - Operating Segments [Member]	1 Months Ended			5 Months Ended	9 Months Ended		12 Months Ended
	May 31, 2020 USD ($)	Mar. 31, 2020 USD ($)	Feb. 29, 2020 USD ($)	May 27, 2020 USD ($) MBoe	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2019 MBoe
Australia West Assets [Member] \| Asia Pacific [Member]
Assets Sold
Proceeds from asset dispositions	$ 765,000,000
Before-tax gain (loss) on disposition					$ (587,000,000)
Disposition, 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)	$ (222,000,000)
Segment which includes disposition					Asia Pacific
Barossa project [Member] \| Asia Pacific [Member]
Assets Sold
Production \| MBoe				43
Barossa project [Member] \| Asia Pacific [Member] \| Scenario Plan [Member]
Assets Sold
Proceeds from asset dispositions	$ 200,000,000
Waddell Ranch [Member] \| Lower 48 Segment
Assets Sold
Proceeds from asset dispositions			$ 184,000,000
Before-tax gain (loss) on disposition			$ 0
Production \| MBoe							15
Segment which includes disposition					Lower 48
Niobrara [Member] \| Lower 48 Segment
Assets Sold
Proceeds from asset dispositions		$ 359,000,000
Before-tax gain (loss) on disposition		38,000,000
Disposition, Net carrying value		397,000,000
Disposition, PP&E		433,000,000
Asset Retirement Obligation of held for sale or sold		$ 34,000,000
Disposition, Before-tax earnings					$ 22,000,000	$ 7,000,000
Production \| MBoe							15
Segment which includes disposition					Lower 48