Capitalized Exploratory Well Costs (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Capitalized Exploratory Well Costs [Abstract]
Capitalized Exploratory Well Costs, Beginning of Period	$ 1,301		$ 900		$ 696
Additions to Capitalized Exploratory Well Costs Pending Determination of Proved Reserves	316		581		360
Reclassified to Proved Oil and Gas Properties Based on Determination of Proved Reserves or to Assets Held for Sale(1)	(196)	[1]	(177)	[1]	(18)	[1]
Capitalized Exploratory Well Costs Charged to Expense	(84)	[2]	(3)	[2]	(114)	[2]
Other	0	[3]	0	[3]	(24)	[3]
Exploratory Well Costs Capitalized for a Period of One Year or Less	247		568		355
Capitalized Exploratory Well Costs that Have Been Capitalized for Period Greater than One Year	1,090		733		545
Capitalized Exploratory Well Costs,	1,337		1,301		900
Number of Projects with Exploratory Well Costs That Have Been Capitalized for a Period Greater Than One Year Since Commencement of Drilling	13		13		14
Capitalized Exploratory Well Costs, End of Period	$ 1,337		$ 1,301		$ 900

[1] The 2014 amount primarily relates to the Dantzler well (deepwater Gulf of Mexico), for which we sanctioned a development plan, and the Tanin and Karish wells (offshore Israel), which were reclassified to assets held for sale. The 2013 amount relates primarily to Gunflint (deepwater Gulf of Mexico), for which we sanctioned a development plan.

[2] The 2014 amount relates to non-core onshore US exploratory well costs and the Scotia exploratory well (offshore Falkland Islands) which were determined to be non-commercial. The 2012 amount primarily represents deepwater Gulf of Mexico exploratory well costs.

[3] The 2012 amount relates to North Sea exploratory well costs included in discontinued operations. See Note 3. Property Transactions.