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				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Asset Impairment Charges [Abstract]
Impaired of Oil and Gas Properties	$ 33		$ 63		$ 164		$ 63
Discount Rate for Impairment Model	10.00%		10.00%		10.00%		10.00%
Quoted Prices in Active Markets (Level 1)
Asset Impairment Charges [Abstract]
Impaired of Oil and Gas Properties	0		0		0		0
Significant Other Observable Inputs (Level 2)
Asset Impairment Charges [Abstract]
Impaired of Oil and Gas Properties	0		0		0		0
Significant Unobservable Inputs (Level 3)
Asset Impairment Charges [Abstract]
Impaired of Oil and Gas Properties	9		75		23		75
Net Book Value
Asset Impairment Charges [Abstract]
Impaired of Oil and Gas Properties	$ 42	[1]	$ 138	[1]	$ 187	[1]	$ 138

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