Asset Impairments - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Impaired Long-Lived Assets Held and Used [Line Items]
Asset Impairments		$ 70	$ 92	$ 533
Other (Onshore US)
Impaired Long-Lived Assets Held and Used [Line Items]
Asset Impairments				481
Gulf of Mexico and Eastern Mediterranean
Impaired Long-Lived Assets Held and Used [Line Items]
Asset Impairments				47
Abandonment and Other Costs
Impaired Long-Lived Assets Held and Used [Line Items]
Asset Impairments				$ 5
Leviathan-1 Deep
Impaired Long-Lived Assets Held and Used [Line Items]
Asset Impairments	$ 88