Segment Information - Net Properties and Equipment by Geographic Area Table (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues from External Customers and Long-Lived Assets [Line Items]
Net properties and equipment	$ 41,589	$ 40,929	$ 38,398
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net properties and equipment	37,186	35,486
Algeria [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net properties and equipment	1,431	1,582
Other International [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Net properties and equipment	$ 2,972	$ 3,861