Accounting for Suspended Exploratory Wells (Details Textual) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011 Project Y Well	Dec. 31, 2010 Project	Dec. 31, 2009 Project
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Capitalized Exploratory Well Costs that Have Been Capitalized for Period Greater than One Year, Total	$ 1,877	$ 2,299	$ 1,871
Number of projects with exploratory well costs that have been capitalized for a period greater than one year	47	53	46
Expected period for decision on the recognition of proved reserves	3
Accounting for Suspended Exploratory Wells (Textual) [Abstract]
Exploratory well costs capitalized for a period greater than one year	1,877	2,299	1,871
Capitalized Exploratory Well Costs Associated with project sanction approved and construction in progress, with initial recognition of proved reserves expected upon reaching economic producibility	111
Total number of exploratory wells that have been capitalized for period greater Than one year	161
Number of projects with exploratory well costs that have been capitalized for a period greater than one year	47	53	46
Project [Member]
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Number of projects with exploratory well costs that have been capitalized for a period greater than one year	1
Accounting for Suspended Exploratory Wells (Textual) [Abstract]
Number of projects with exploratory well costs that have been capitalized for a period greater than one year	1
Drilling Activity [Member]
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Capitalized Exploratory Well Costs that Have Been Capitalized for Period Greater than One Year, Total	939
Accounting for Suspended Exploratory Wells (Textual) [Abstract]
Exploratory well costs capitalized for a period greater than one year	939
Drilling Activity [Member] | Project [Member]
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Number of projects with exploratory well costs that have been capitalized for a period greater than one year	26
Accounting for Suspended Exploratory Wells (Textual) [Abstract]
Number of projects with exploratory well costs that have been capitalized for a period greater than one year	26
No Drilling Activity [Member]
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Capitalized Exploratory Well Costs that Have Been Capitalized for Period Greater than One Year, Total	938
Accounting for Suspended Exploratory Wells (Textual) [Abstract]
Exploratory well costs capitalized for a period greater than one year	938
No Drilling Activity [Member] | Project [Member]
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Number of projects with exploratory well costs that have been capitalized for a period greater than one year	21
Accounting for Suspended Exploratory Wells (Textual) [Abstract]
Number of projects with exploratory well costs that have been capitalized for a period greater than one year	21
Development Concept Under Review by Government [Member]
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Capitalized Exploratory Well Costs that Have Been Capitalized for Period Greater than One Year, Total	283
Accounting for Suspended Exploratory Wells (Textual) [Abstract]
Exploratory well costs capitalized for a period greater than one year	283
Development Concept Under Review by Government [Member] | Project [Member]
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Number of projects with exploratory well costs that have been capitalized for a period greater than one year	5
Accounting for Suspended Exploratory Wells (Textual) [Abstract]
Number of projects with exploratory well costs that have been capitalized for a period greater than one year	5
Miscellaneous Activities [Member]
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Capitalized Exploratory Well Costs that Have Been Capitalized for Period Greater than One Year, Total	14
Accounting for Suspended Exploratory Wells (Textual) [Abstract]
Exploratory well costs capitalized for a period greater than one year	14
Miscellaneous Activities [Member] | Project [Member]
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Number of projects with exploratory well costs that have been capitalized for a period greater than one year	2
Accounting for Suspended Exploratory Wells (Textual) [Abstract]
Number of projects with exploratory well costs that have been capitalized for a period greater than one year	2
Reviewing Development Alternatives [Member]
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Capitalized Exploratory Well Costs that Have Been Capitalized for Period Greater than One Year, Total	322
Accounting for Suspended Exploratory Wells (Textual) [Abstract]
Exploratory well costs capitalized for a period greater than one year	322
Reviewing Development Alternatives [Member] | Project [Member]
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Number of projects with exploratory well costs that have been capitalized for a period greater than one year	6
Accounting for Suspended Exploratory Wells (Textual) [Abstract]
Number of projects with exploratory well costs that have been capitalized for a period greater than one year	6
Undergoing Front End Engineering and Design with Final Investment Decision Expected [Member]
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Capitalized Exploratory Well Costs that Have Been Capitalized for Period Greater than One Year, Total	208
Accounting for Suspended Exploratory Wells (Textual) [Abstract]
Exploratory well costs capitalized for a period greater than one year	$ 208
Undergoing Front End Engineering and Design with Final Investment Decision Expected [Member] | Project [Member]
Projects with Exploratory Well Costs Capitalized for More than One Year [Line Items]
Number of projects with exploratory well costs that have been capitalized for a period greater than one year	7
Undergoing front-end engineering and design with final investment decision expected in three years	3
Accounting for Suspended Exploratory Wells (Textual) [Abstract]
Number of projects with exploratory well costs that have been capitalized for a period greater than one year	7