Geographic Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenues	$ 8,602	$ 9,923	$ 9,732	$ 8,413	$ 8,399	$ 9,816	$ 9,153	$ 7,747	$ 36,670	$ 35,115	$ 31,755
Domestic [Member]
Revenues									23,827	22,722	20,744
Atlantic [Member]
Revenues									6,481	6,486	5,931
Pacific [Member]
Revenues									3,979	3,644	3,283
Latin America [Member]
Revenues									$ 2,383	$ 2,263	$ 1,797