Fair Value Measurements and Disclosures of Assets and Liabilities Measured on a Nonrecurring Basis (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Asset Impairment Charges [Abstract]
Impairment of Oil and Gas Properties	$ 97		$ 0
Discount Rate for Impairment Model	10.00%		10.00%
Quoted Prices in Active Markets (Level 1)
Asset Impairment Charges [Abstract]
Impairment of Oil and Gas Properties	0		0
Significant Other Observable Inputs (Level 2)
Asset Impairment Charges [Abstract]
Impairment of Oil and Gas Properties	0		0
Significant Unobservable Inputs (Level 3)
Asset Impairment Charges [Abstract]
Impairment of Oil and Gas Properties	6		0
Net Book Value
Asset Impairment Charges [Abstract]
Impairment of Oil and Gas Properties	$ 103	[1]	$ 0

[1] Amount represents net book value at the date of assessment.