Property, Plant and Equipment - Net Changes in Capitalized Exploratory Well Costs (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) Well	Dec. 31, 2018 USD ($) Well	Dec. 31, 2017 USD ($) Well
Capitalized Exploratory Well Costs [Abstract]
Beginning balance	$ 418	$ 304	$ 597
Additions to capitalized exploratory well costs pending the determination of proved reserves	224	128	116
Reclassifications to wells, facilities and equipment based on the determination of proved reserves	(58)	0	(165)
Capitalized exploratory well costs charged to expense	0	(14)	(268)
Dispositions and other	0	0	24
Ending balance	$ 584	$ 418	$ 304
Number of Wells at December 31 | Well	31	24	12