Summary of Significant Accounting Policies (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Accounting Policies [Abstract]
Ownership Interest Percent Threshold to Consolidate	50.00%
Contract carrier agreements, number of contract carriers	9
Residual Values For Owned Spare Parts As Percentage Of Cost	5.00%
Depreciation, Nonproduction	$ 1,400,000,000	$ 1,400,000,000	$ 1,300,000,000
Capitalized Computer Software, Amortization	64,000,000	71,000,000	95,000,000
Capitalized Computer Software, Net	200,000,000	153,000,000
Goodwill	9,794,000,000	9,794,000,000
Intangible Assets, Net (Excluding Goodwill)	4,751,000,000	4,749,000,000
Advertising Expense	$ 214,000,000	$ 169,000,000	$ 176,000,000