Supplementary Oil and Gas Disclosure (Unaudited) - Other Costs Incurred (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Capitalized costs of oil and gas properties not included in total costs incurred	$ 23	$ 2,094	$ 434
Domestic [Member]
Capitalized Costs Exceeding Ceiling - Effect on Full cost Pool	0	1,488	0
Property sales excluded from cost incurred	$ 23	$ 606	$ 434