Properties and Equipment (Detail) (USD $)	Dec. 31, 2014		Dec. 31, 2013
Property, Plant, and Equipment [Line Items]
Cost of properties and equipment	$ 75,107,000,000		$ 71,244,000,000
Oil and Gas Exploration and Production Reporting Segment [Member]
Property, Plant, and Equipment [Line Items]
Cost of properties and equipment	63,674,000,000	[1]	61,302,000,000	[1]
Costs associated with unproved properties	5,100,000,000		6,900,000,000
Midstream Reporting Segment [Member]
Property, Plant, and Equipment [Line Items]
Cost of properties and equipment	8,647,000,000		7,285,000,000
Marketing Reporting Segment [Member]
Property, Plant, and Equipment [Line Items]
Cost of properties and equipment	0		9,000,000
Other and Intersegment Eliminations [Member]
Property, Plant, and Equipment [Line Items]
Cost of properties and equipment	$ 2,786,000,000		$ 2,648,000,000

[1] Includes costs associated with unproved properties of $5.1 billion at December 31, 2014, and $6.9 billion at December 31, 2013.