Property, Plant and Equipment (Details 3) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Projects that have Exploratory Well Costs that have been Capitalized for Period Greater than One Year, Number of Projects	3	7	6
Amounts capitalized greater than one year after completion of drilling	$ 126	$ 281	$ 229
GABON
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Amounts capitalized greater than one year after completion of drilling	66
EQUATORIAL GUINEA
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Amounts capitalized greater than one year after completion of drilling	22
CANADA
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Amounts capitalized greater than one year after completion of drilling	$ 38