Capitalized Exploratory Well Costs - Net Changes in Capitalized Exploratory Well Costs (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($)
Capitalized Exploratory Well Costs [Abstract]
Beginning balance	$ 1,415
Additions to capitalized exploratory well costs pending the determination of proved reserves	60
Capitalized exploratory well costs charged to expense	(25)
Ending balance	$ 1,450