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Impairments - Impairments of Unproved Properties (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property, Plant, and Equipment [Line Items]
Impairment of unproved properties	$ 1,245	$ 864	$ 1,544
U.S. Onshore Properties [Member]
Property, Plant, and Equipment [Line Items]
Impairment of unproved properties			721
Gulf of Mexico Properties [Member]
Property, Plant, and Equipment [Line Items]
Impairment of unproved properties			$ 124

The adjustment to expense previously capitalized costs of drilling exploratory wells when proved reserves are not found or when the entity obtains information that raises substantial doubt about the economic or operational viability of the project.

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