Dispositions - International E&P Segment (Details) - USD ($) $ in Millions	3 Months Ended				12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal of assets, net of cash transferred to the buyer					$ 1,264	$ 1,787	$ 1,219
International | Non-Core Property, Second Quarter 2018 Agreement [Member] | Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percentage interest in property	15.00%
Disposal of assets, net of cash transferred to the buyer	$ 63
Assets	58				58
Liabilities	$ 17				$ 17
International | Marathon Oil Libya Limited [Member] | Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percentage interest in property			16.33%
Disposal of assets, net of cash transferred to the buyer			$ 450
Gain (loss) on disposal			$ 255
International | Non-Core Property, Third Quarter 2017 Agreement [Member] | Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal of assets, net of cash transferred to the buyer				$ 53
Gain (loss) on disposal		$ (18)