Segment Information - Net Properties and Equipment by Geographic Area Table (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues from External Customers and Long-Lived Assets [Line Items]
Net properties and equipment	$ 33,751	$ 41,589	$ 40,929
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net properties and equipment	29,625	37,186
Algeria [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net properties and equipment	1,271	1,431
Other International [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net properties and equipment	$ 2,855	$ 2,972