Property, Plant & Equipment (Details 2) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011
Capitalized Exploratory Well Costs [Abstract]
Capitalized exploratory well costs that have been capitalized for period greater than one year	$ 1,503
Year 2010 [Member]
Capitalized Exploratory Well Costs [Abstract]
Capitalized exploratory well costs that have been capitalized for period greater than one year	423
Year 2009 [Member]
Capitalized Exploratory Well Costs [Abstract]
Capitalized exploratory well costs that have been capitalized for period greater than one year	448
Year 2008 [Member]
Capitalized Exploratory Well Costs [Abstract]
Capitalized exploratory well costs that have been capitalized for period greater than one year	392
Year 2007 [Member]
Capitalized Exploratory Well Costs [Abstract]
Capitalized exploratory well costs that have been capitalized for period greater than one year	72
Year 2006 [Member]
Capitalized Exploratory Well Costs [Abstract]
Capitalized exploratory well costs that have been capitalized for period greater than one year	$ 168