Leases (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Operating Leased Assets [Line Items]
Special facility revenue bonds	$ 1,500,000,000
Mandatory tender provisions	177,000,000
Operating Leases, rent expense	1,600,000,000	1,500,000,000	1,300,000,000
Number of aircraft operating leased under trusts	70
Operating leases future minimum payments due leased under trusts	794,000,000
Non-cash charges related to sale/leaseback transactions	31,000,000
Revenue Bonds [Member]
Operating Leased Assets [Line Items]
Operating lease future payments to repurchase bonds	3,200,000,000
Boeing 737-800 NG Aircraft [Member]
Operating Leased Assets [Line Items]
Number of aircrafts deliveries under sale leaseback transactions	36
Vintage Aircraft [Member]
Operating Leased Assets [Line Items]
Nonrecurring charges under sale leaseback transaction of vintage aircraft			88,000,000
Jet Aircraft [Member]
Operating Leased Assets [Line Items]
Number of aircraft committed to operating leases	203
Number of aircraft committed to capital leases	60
Turboprop Aircraft [Member]
Operating Leased Assets [Line Items]
Number of aircraft committed to operating leases	36
Minimum [Member]
Operating Leased Assets [Line Items]
Leases renewal at the fair market value (in years)	1
Maximum [Member]
Operating Leased Assets [Line Items]
Leases renewal at the fair market value (in years)	5
2014 [Member] | Revenue Bonds [Member]
Operating Leased Assets [Line Items]
Operating lease future payments to repurchase bonds	112,000,000
2015 [Member] | Revenue Bonds [Member]
Operating Leased Assets [Line Items]
Operating lease future payments to repurchase bonds	$ 65,000,000