Fair Value Measurements and Disclosures of Assets and Liabilities Measured on a Nonrecurring Basis (Details 2) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Asset Impairment Charges [Abstract]
Impaired of Oil and Gas Properties		$ 0	$ 15	$ 0	$ 43
Oil and Gas Property, Full Cost Method, Net	[1]	0	15	0	43
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		$ 0	$ 0	$ 0	$ 0

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