GENERAL AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - MILEAGE PLAN (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Mileage Plan [Line Items]
Other accrued liabilities	$ 661	$ 585
Other liabilities	362	327
Deferred revenue	431	374
Deferred revenue from Mileage Plan awards issued but not yet flown	37	33
Passenger revenues	4,793	4,579	$ 4,267
Other-net revenues	697	675	584
Special Revenue	0	0	192
Total Operating Revenues	5,598	5,368	5,156
Revenue From Mileage Plan [Member]
Mileage Plan [Line Items]
Passenger revenues	267	246	208
Other-net revenues	329	295	256
Special Revenue	0	0	192
Total Operating Revenues	596	541	656
Commission revenue	280	261	$ 213
Liabilities From Mileage Plan [Member]
Mileage Plan [Line Items]
Other accrued liabilities	368	343
Other liabilities	19	20
Deferred revenue	427	367
Liabilities	$ 814	$ 730