Properties and Equipment - Suspended Exploratory Drilling Costs by Region Table (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Capitalized Exploratory Well Costs [Line Items]
Suspended exploratory drilling costs	$ 1,353	$ 935	$ 579	$ 279
Year Costs Incurred 2011 [Member]
Capitalized Exploratory Well Costs [Line Items]
Suspended exploratory drilling costs	559
Year Costs Incurred 2010 [Member]
Capitalized Exploratory Well Costs [Line Items]
Suspended exploratory drilling costs	376
Year Costs Incurred 2009 and Prior [Member]
Capitalized Exploratory Well Costs [Line Items]
Suspended exploratory drilling costs	418
United States Onshore [Member]
Capitalized Exploratory Well Costs [Line Items]
Suspended exploratory drilling costs	110
United States Onshore [Member] | Year Costs Incurred 2011 [Member]
Capitalized Exploratory Well Costs [Line Items]
Suspended exploratory drilling costs	96
United States Onshore [Member] | Year Costs Incurred 2010 [Member]
Capitalized Exploratory Well Costs [Line Items]
Suspended exploratory drilling costs	4
United States Onshore [Member] | Year Costs Incurred 2009 and Prior [Member]
Capitalized Exploratory Well Costs [Line Items]
Suspended exploratory drilling costs	10
United States Offshore [Member]
Capitalized Exploratory Well Costs [Line Items]
Suspended exploratory drilling costs	233
United States Offshore [Member] | Year Costs Incurred 2011 [Member]
Capitalized Exploratory Well Costs [Line Items]
Suspended exploratory drilling costs	(5)
United States Offshore [Member] | Year Costs Incurred 2010 [Member]
Capitalized Exploratory Well Costs [Line Items]
Suspended exploratory drilling costs	60
United States Offshore [Member] | Year Costs Incurred 2009 and Prior [Member]
Capitalized Exploratory Well Costs [Line Items]
Suspended exploratory drilling costs	178
International [Member]
Capitalized Exploratory Well Costs [Line Items]
Suspended exploratory drilling costs	1,010
International [Member] | Year Costs Incurred 2011 [Member]
Capitalized Exploratory Well Costs [Line Items]
Suspended exploratory drilling costs	468
International [Member] | Year Costs Incurred 2010 [Member]
Capitalized Exploratory Well Costs [Line Items]
Suspended exploratory drilling costs	312
International [Member] | Year Costs Incurred 2009 and Prior [Member]
Capitalized Exploratory Well Costs [Line Items]
Suspended exploratory drilling costs	$ 230