Impairments - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant, and Equipment [Line Items]
Impairment of unproved properties	$ 2,221	$ 613	$ 2,267
Unproved Gulf of Mexico Properties [Member]
Property, Plant, and Equipment [Line Items]
Impairment of unproved properties	610	72	66
Gulf Of Mexico, Shenandoah Project [Member]
Property, Plant, and Equipment [Line Items]
Impairment of unproved properties	463
Unproved International Properties [Member]
Property, Plant, and Equipment [Line Items]
Impairment of unproved properties	$ 88	$ 92
Unproved Greater Natural Buttes Properties [Member]
Property, Plant, and Equipment [Line Items]
Impairment of unproved properties			935
Unproved Utica Properties [Member]
Property, Plant, and Equipment [Line Items]
Impairment of unproved properties			$ 109