Capitalized Exploratory Well Costs - Net Changes in Capitalized Exploratory Well Costs (Detail) $ in Millions	6 Months Ended
	Jun. 30, 2015 USD ($)
Capitalized Exploratory Well Costs [Abstract]
Beginning balance	$ 1,416
Additions to capitalized exploratory well costs pending the determination of proved reserves	281
Reclassifications to wells, facilities and equipment based on the determination of proved reserves	(72)
Capitalized exploratory well costs charged to expense	(120)
Ending balance	$ 1,505