Capitalized Exploratory Well Costs (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2012		Dec. 31, 2011
Capitalized Exploratory Well Costs [Abstract]
Capitalized Exploratory Well Costs, Beginning of Period	$ 696
Additions to Capitalized Exploratory Well Costs Pending Determination of Proved Reserves	164
Reclassified to Proved Oil and Gas Properties Based on Determination of Proved Reserves	(27)
Capitalized Exploratory Well Cost, Charged to Expense	(108)	[1]
Other	(19)	[2]
Capitalized Exploratory Well Costs, End of Period	706
Exploratory Well Costs capitalized for a Period of One Year or Less	301		318
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	405		378
Number of Projects with Exploratory Well Costs That Have Been Capitalized for a Period Greater Than One Year Since Commencement of Drilling	9		9
Capitalized Exploratory Well Costs, End of Period	706
Projects with Exploratory Well Costs Capitalized for More than One Year Since The Commencement of Drilling [Line Items]
Suspended since 2009 & prior	219
Suspended Since 2010	56
Suspended Since 2011	130
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	405		378
Blocks O And I Offshore Equatorial Guinea
Capitalized Exploratory Well Costs [Abstract]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	156
Projects with Exploratory Well Costs Capitalized for More than One Year Since The Commencement of Drilling [Line Items]
Suspended since 2009 & prior	106
Suspended Since 2010	6
Suspended Since 2011	44
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	156
YoYo Offshore Cameron
Capitalized Exploratory Well Costs [Abstract]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	45
Projects with Exploratory Well Costs Capitalized for More than One Year Since The Commencement of Drilling [Line Items]
Suspended since 2009 & prior	38
Suspended Since 2010	2
Suspended Since 2011	5
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	45
Leviathan Offshore Israel
Capitalized Exploratory Well Costs [Abstract]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	78
Projects with Exploratory Well Costs Capitalized for More than One Year Since The Commencement of Drilling [Line Items]
Suspended since 2009 & prior	0
Suspended Since 2010	41
Suspended Since 2011	37
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	78
Leviathan-1 Deep Offshore Israel
Capitalized Exploratory Well Costs [Abstract]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	28
Projects with Exploratory Well Costs Capitalized for More than One Year Since The Commencement of Drilling [Line Items]
Suspended since 2009 & prior	0
Suspended Since 2010	0
Suspended Since 2011	28
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	28
Dalit Offshore Israel
Capitalized Exploratory Well Costs [Abstract]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	22
Projects with Exploratory Well Costs Capitalized for More than One Year Since The Commencement of Drilling [Line Items]
Suspended since 2009 & prior	21
Suspended Since 2010	1
Suspended Since 2011	0
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	22
Cyprus A-1 Offshore Cyprus
Capitalized Exploratory Well Costs [Abstract]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	10
Projects with Exploratory Well Costs Capitalized for More than One Year Since The Commencement of Drilling [Line Items]
Suspended since 2009 & prior	0
Suspended Since 2010	0
Suspended Since 2011	10
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	10
Gunflint Deepwater Gulf Of Mexico
Capitalized Exploratory Well Costs [Abstract]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	54
Projects with Exploratory Well Costs Capitalized for More than One Year Since The Commencement of Drilling [Line Items]
Suspended since 2009 & prior	54
Suspended Since 2010	0
Suspended Since 2011	0
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	54
Other - 2 Projects of $10 million or less
Capitalized Exploratory Well Costs [Abstract]
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	12
Projects with Exploratory Well Costs Capitalized for More than One Year Since The Commencement of Drilling [Line Items]
Suspended since 2009 & prior	0
Suspended Since 2010	6
Suspended Since 2011	6
Exploratory Well Costs Capitalized for a Period Greater Than One Year Since Commencement of Drilling	$ 12

[1] Amount primarily represents the Deep Blue exploratory well (deepwater Gulf of Mexico) costs capitalized prior to December 31, 2011. Although hydrocarbons were found in both the initial exploration well and subsequent sidetrack, we and our partners decided not to proceed with additional appraisal activities.

[2] Amount represents the Selkirk exploratory well (North Sea) which, along with our other North Sea assets, was reclassified to held for sale at June 30, 2012. See Note 3. Acquisitions and Divestitures.