GENERAL AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - MILEAGE PLAN (DETAILS) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Mileage Plan [Line Items]
Other accrued liabilities	$ 539	$ 513
Other liabilities	334	148
Deferred revenue	443	410
Deferred revenue from Mileage Plan awards issued but not yet flown	39	39
Passenger revenues	4,030	3,708	3,266
Other-net revenues	516	501	460
Total Operating Revenues	4,657	4,318	3,832
Liabilities From Mileage Plan [Member]
Mileage Plan [Line Items]
Other accrued liabilities	285	271
Other liabilities	17	17
Deferred revenue	428	392
Liabilities	730	680
Revenue From Mileage Plan [Member]
Mileage Plan [Line Items]
Passenger revenues	183	201	190
Other-net revenues	209	195	183
Total Operating Revenues	392	396	373
Commission revenue	$ 143	$ 138	$ 124