Property, Plant and Equipment (Details 2) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Property, Plant and Equipment [Abstract]
Amounts capitalized less than one year after completion of drilling				$ 352	$ 484	$ 512
Amounts capitalized greater than one year after completion of drilling				85	126	281
Total deferred exploratory well costs	$ 610	$ 793	$ 617	$ 437	$ 610	$ 793
Projects that have Exploratory Well Costs that have been Capitalized for Period Greater than One Year, Number of Projects				2	3	7
Increase (Decrease) in Capitalized Exploratory Well Costs that are Pending Determination of Proved Reserves [Roll Forward]
Beginning balance	610	793	617
Additions	610	647	624
Dry well expense	(148)	(45)	(25)
Transfers to development	(635)	(579)	(414)
Dispositions				$ 0	$ (206)	$ (9)
Ending balance	$ 437	$ 610	$ 793