Property, Plant and Equipment (Details 2) $ in Millions	Dec. 31, 2018 USD ($) project	Dec. 31, 2017 USD ($) project	Dec. 31, 2016 USD ($) project	Dec. 31, 2015 USD ($)
Property, Plant and Equipment [Abstract]
Amounts capitalized less than one year after completion of drilling	$ 297	$ 263	$ 131
Amounts capitalized greater than one year after completion of drilling	0	32	118
Total deferred exploratory well costs	$ 297	$ 295	$ 249	$ 437
Projects that have Exploratory Well Costs that have been Capitalized for Period Greater than One Year, Number of Projects | project	0	1	3