Acquisitions, Divestitures, and Assets Held for Sale - Divestitures (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Property, Plant, and Equipment [Line Items]
Proceeds from divestitures	$ 567	$ 657	$ 555
Net gains (losses) on divestitures	(470)	(71)	22
Assets Held For Use [Member]
Property, Plant, and Equipment [Line Items]
Proceeds from divestitures	509	433
Net gains (losses) on divestitures	234	(43)
Assets Held For Use [Member] | Peregrino Field [Member]
Property, Plant, and Equipment [Line Items]
Proceeds from divestitures			$ 419