GENERAL AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - MILEAGE PLAN (DETAILS) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Mileage Plan [Line Items]
Other accrued liabilities	$ 629	$ 624
Other liabilities	327	308
Deferred revenue	374	335
Deferred revenue from Mileage Plan awards issued but not yet flown	33	31
Passenger revenues	4,579	4,267	4,030
Other-net revenues	675	584	516
Special Revenue	0	192	0
Total Operating Revenues	5,368	5,156	4,657
Revenue From Mileage Plan [Member]
Mileage Plan [Line Items]
Passenger revenues	246	208	183
Other-net revenues	295	256	209
Special Revenue	0	192	0
Total Operating Revenues	541	656	392
Commission revenue	261	213	143
Liabilities From Mileage Plan [Member]
Mileage Plan [Line Items]
Other accrued liabilities	343	314
Other liabilities	20	19
Deferred revenue	367	323
Liabilities	$ 730	$ 656