Suspended Exploratory Well Costs - Rollforward (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Increase (Decrease) in Capitalized Exploratory Well Costs that are Pending Determination of Proved Reserves [Roll Forward]
Balance at January 1	$ 2,062	$ 1,353	$ 935
Additions pending the determination of proved reserves	848	960	572
Divestitures	(48)	0	0
Reclassifications to proved properties	(507)	(129)	(116)
Charges to exploration expense	(123)	(122)	(38)
Balance at December 31	$ 2,232	$ 2,062	$ 1,353