Impairments - Impairments by Segment Table (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Impaired Long Lived Assets Held and Used [Line Items]
Total impairments	$ 836,000,000	$ 794,000,000	$ 389,000,000
Oil and Gas Exploration and Production Reporting Segment [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Cost-method investment	3,000,000	11,000,000	13,000,000
Oil and Gas Exploration and Production Reporting Segment [Member] | U.S. Onshore Properties [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Long-lived assets held for use	545,000,000	142,000,000	259,000,000
Oil and Gas Exploration and Production Reporting Segment [Member] | Gulf of Mexico Properties [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Long-lived assets held for use	276,000,000	562,000,000	104,000,000
Oil and Gas Exploration and Production Reporting Segment [Member] | Other U.S. Onshore Properties [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Long-lived assets held for use	0
Midstream Reporting Segment [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Long-lived assets held for use	$ 12,000,000	$ 79,000,000	$ 13,000,000