Capitalized Exploratory Well Costs (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2016	Dec. 31, 2015
Extractive Industries [Abstract]
Capitalized exploratory well costs	$ 262	$ 245
Capitalized exploratory well costs that have been capitalized for period greater than one year	$ 93	$ 61
Increase of capitalized exploratory well costs	32