Impairments (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Asset impairments			$ 1,160	$ 206	$ 70
Fair value	$ 600		600
Undeveloped leasehold costs	2,152	$ 2,373	2,152	2,373	2,922
Goodwill impairment		1,300	$ 0	1,281	0
Gulf of Mexico
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Asset impairments				$ 168
Certain midstream assets
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Asset impairments	$ 38
Impairment charge		$ 37
Troubadour
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Asset impairments					$ 70