Exploratory Costs (Schedule Of Capitalized Exploratory Well And Project Activity) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2014	Dec. 31, 2013
Beginning capitalized exploratory costs	$ 322	$ 159
Additions to exploratory costs pending the determination of proved reserves	586	1,275
Reclassification due to determination of proved reserves	(466)	(941)
Capitalized Exploratory Well Cost Assets Disposition	(16)	(52)
Exploratory well costs charged to exploration expense	(1)	(5)
Ending capitalized exploratory costs	424	424
Capitalized exploratory costs that have been suspended, One year or less	416	416	116
Capitalized Exploratory Well Costs that Have Been Capitalized for Period Greater than One Year	8	8	43
Number of projects with exploratory costs that have been suspended for a period greater than one year	3	3	1
Capitalized exploratory costs [Member]
Impairment of oil and gas properties	$ (1)	$ (12)