Property, Plant and Equipment Property, Plant and Equipment (Details 3) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Increase (Decrease) in Capitalized Exploratory Well Costs that are Pending Determination of Proved Reserves [Roll Forward]
Beginning balance	$ 295	$ 249	$ 437
Additions	262	212	299
Charges to expense	(35)	(64)	(23)
Transfers to development	(197)	(102)	(388)
Dispositions	(28)	0	(76)
Ending balance	297	295	249
Amounts capitalized greater than one year after completion of drilling	0	32	$ 118
Rodo
Increase (Decrease) in Capitalized Exploratory Well Costs that are Pending Determination of Proved Reserves [Roll Forward]
Charges to expense	$ (32)
Diaba
Increase (Decrease) in Capitalized Exploratory Well Costs that are Pending Determination of Proved Reserves [Roll Forward]
Charges to expense		$ (64)