Capitalized Exploratory Well Costs (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Exploratory Wells Drilled [Line Items]
Farm down				35.00%
Capitalized costs charged to expense	$ (525)	$ (88)	$ (84)
Increase (Decrease) in Capitalized Exploratory Well Costs that are Pending Determination of Proved Reserves [Roll Forward]
Capitalized Exploratory Well Costs, Beginning of Period	1,353	1,337	1,301
Additions to Capitalized Exploratory Well Costs Pending Determination of Proved Reserves	84	123	316
Divestitures and Other (1)	(143)	0	0
Capitalized Exploratory Well Costs Charged to Expense	(1)	(19)	(196)
Capitalized Exploratory Well Costs, End of Period	768	1,353	1,337
Exploratory Well Costs Capitalized for a Period of One Year or Less				$ 69	$ 95	$ 247
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling				699	1,258	1,090
Capitalized Exploratory Well Costs,	$ 1,353	$ 1,337	$ 1,301	$ 768	$ 1,353	$ 1,337
Number of Projects with Exploratory Well Costs That Have Been Capitalized for a Period Greater Than One Year Since Commencement of Drilling				10	14	13