Capitalized Exploratory Well Costs - Capitalized Exploratory Well Costs Rollforward (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Increase (Decrease) in Capitalized Exploratory Well Costs that are Pending Determination of Proved Reserves [Roll Forward]
Capitalized exploratory well costs, Beginning Balance	$ 245	$ 849	$ 630
Additions pending determination of proved reserves	249	382	622
Divestitures and other	0	(557)	(54)
Reclassifications to proved properties	(211)	(369)	(207)
Charged to exploration expense	(19)	(60)	(142)
Capitalized exploratory well costs, Ending Balance	$ 264	$ 245	849
Australia [Member]
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Assets held for sale			$ 49