Segment Information - Financial Information by Major Geographic Area (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Segment Reporting Information [Line Items]
Operating revenues	$ 22,284	$ 23,381	$ 21,451
Property, plant and equipment (net)	28,766	28,478	24,386
United States [Member]
Segment Reporting Information [Line Items]
Operating revenues	16,589	16,588	14,916
Property, plant and equipment (net)	16,082	13,914	11,172
Europe [Member]
Segment Reporting Information [Line Items]
Operating revenues	1,336	2,530	3,137
Property, plant and equipment (net)	7,475	8,172	6,826
Africa [Member]
Segment Reporting Information [Line Items]
Operating revenues	2,736	2,484	1,782
Property, plant and equipment (net)	2,310	2,517	2,355
Asia and Other [Member]
Segment Reporting Information [Line Items]
Operating revenues	1,623	1,779	1,616
Property, plant and equipment (net)	$ 2,899	$ 3,875	$ 4,033