Geographic Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues from External Customers and Long-Lived Assets [Line Items]
Operating revenue	$ 9,647	$ 11,178	$ 10,621	$ 8,916	$ 9,076	$ 10,490	$ 9,707	$ 8,500	$ 40,362	$ 37,773	$ 36,670
Domestic
Revenues from External Customers and Long-Lived Assets [Line Items]
Operating revenue									26,898	24,857	23,989
Atlantic
Revenues from External Customers and Long-Lived Assets [Line Items]
Operating revenue									6,757	6,446	6,329
Pacific
Revenues from External Customers and Long-Lived Assets [Line Items]
Operating revenue									3,948	4,086	4,198
Latin America
Revenues from External Customers and Long-Lived Assets [Line Items]
Operating revenue									$ 2,759	$ 2,384	$ 2,154