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				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Asset Impairment Charges [Abstract]
Impaired of Oil and Gas Properties	$ 34		$ 0		$ 131		$ 0
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	8		0		14		0
Net Book Value
Asset Impairment Charges [Abstract]
Impaired of Oil and Gas Properties	$ 42	[1]	$ 0	[1]	$ 145	[1]	$ 0

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