Capitalized Exploratory Well Costs (Details Textual) (USD $) In Millions, unless otherwise specified	9 Months Ended
Sep. 30, 2011
Capitalized Exploratory Well Costs (Textual) [Abstract]
Capitalized exploratory well cost charge to expense	$ 132
Capitalized exploratory well costs that have been capitalized for period greater than one year	$ 1,320
Capitalized well costs attributable to Pony and Tubular Bells projects	38.00%
Capitalized well costs attributable to Block WA-390-P offshore Western Australia	30.00%
Capitalized well costs attributable to Area 54 offshore Libya	20.00%

The amount of exploratory well costs that have been capitalized for a period of greater than one year after the completion of drilling.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS19-1

-Paragraph 10

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 932

-SubTopic 235

-Section 50

-Paragraph 1B

-Subparagraph b

-URI http://asc.fasb.org/extlink&oid=6821537&loc=SL6806780-109447

Name:	us-gaap_CapitalizedExploratoryWellCostsThatHaveBeenCapitalizedForPeriodGreaterThanOneYear
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant