Quarterly Financial Data (Unaudited) (Details 1) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012
Quarterly Financial Information, Quarterly Charges and Credits, Amount Affecting Comparability	$ 7,921	$ 157	$ (159)	$ (78)	$ (231)	$ 279	$ (754)	$ 163
Facilities, fleet and other [Member]
Quarterly Financial Information, Quarterly Charges and Credits, Amount Affecting Comparability	(160)	(128)	(34)	(102)	(122)	(122)	(22)	(27)
MTM adjustments [Member]
Quarterly Financial Information, Quarterly Charges and Credits, Amount Affecting Comparability	92	285	(125)	24	(3)	440	(561)	151
Release of tax valuation allowance [Member]
Quarterly Financial Information, Quarterly Charges and Credits, Amount Affecting Comparability	7,989	0	0	0
Severance and related costs [Member]
Quarterly Financial Information, Quarterly Charges and Credits, Amount Affecting Comparability					0	(66)	(171)	0
Routes and slots [Member]
Quarterly Financial Information, Quarterly Charges and Credits, Amount Affecting Comparability					0	39	0	39
Loss on extingushment of debt [Member]
Quarterly Financial Information, Quarterly Charges and Credits, Amount Affecting Comparability					$ (106)	$ (12)	$ 0	$ 0