Impairments - Impairments of Unproved Properties (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2015	Sep. 30, 2014
Property, Plant, and Equipment [Line Items]
Impairment of unproved properties		$ 1,993	$ 743
U.S. Onshore Properties [Member] | Unproved Utica Properties [Member]
Property, Plant, and Equipment [Line Items]
Impairment of unproved properties	$ 109
U.S. Onshore Properties [Member] | Unproved Greater Natural Buttes Properties [Member]
Property, Plant, and Equipment [Line Items]
Impairment of unproved properties		$ 935