OPERATING SEGMENT INFORMATION (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) segment	Sep. 30, 2016 USD ($)
Segment Reporting Information [Line Items]
Number of Operating Segments | segment			3
Capacity purchase arrangements	100.00%		100.00%
Operating revenues
Passenger, Mainline	$ 1,562	$ 1,073	$ 4,390	$ 3,036
Passenger, Regional	262	249	725	682
Total passenger revenue	1,824	1,322	5,115	3,718
CPA revenues	0	0	0	0
Freight and mail	32	31	88	82
Other - net revenue	264	213	768	607
Total Operating Revenues	2,120	1,566	5,971	4,407
Operating expenses
Operating Expenses, Excluding Fuel	1,313	941	3,822	2,706
Economic fuel	368	225	1,051	593
Total Operating Expenses	1,681	1,166	4,873	3,299
Nonoperating Income (Expense)
Interest income	9	7	25	20
Interest expense	(26)	(11)	(77)	(33)
Other	5	6	12	19
Nonoperating Income (Expense) Total	(12)	2	(40)	6
Income (loss) before income tax	427	402	1,058	1,114
Air Group Adjusted [Member]
Operating revenues
Passenger, Mainline	1,562	1,073	4,390	3,036
Passenger, Regional	262	249	725	682
Total passenger revenue	1,824	1,322	5,115	3,718
CPA revenues	0	0	0	0
Freight and mail	32	31	88	82
Other - net revenue	264	213	768	607
Total Operating Revenues	2,120	1,566	5,971	4,407
Operating expenses
Operating Expenses, Excluding Fuel	1,289	919	3,734	2,670
Economic fuel	373	222	1,044	602
Total Operating Expenses	1,662	1,141	4,778	3,272
Nonoperating Income (Expense)
Interest income	9	7	25	20
Interest expense	(26)	(11)	(77)	(33)
Other	5	6	12	19
Nonoperating Income (Expense) Total	(12)	2	(40)	6
Income (loss) before income tax	446	427	1,153	1,141
Alaska Mainline [Member]
Operating revenues
Passenger, Mainline	1,562	1,073	4,390	3,036
Passenger, Regional	0	0	0	0
Total passenger revenue	1,562	1,073	4,390	3,036
CPA revenues	0	0	0	0
Freight and mail	30	30	84	79
Other - net revenue	242	190	708	546
Total Operating Revenues	1,834	1,293	5,182	3,661
Operating expenses
Operating Expenses, Excluding Fuel	1,077	727	3,101	2,107
Economic fuel	328	188	924	512
Total Operating Expenses	1,405	915	4,025	2,619
Nonoperating Income (Expense)
Interest income	11	7	27	19
Interest expense	(23)	(7)	(68)	(23)
Other	5	5	11	15
Nonoperating Income (Expense) Total	(7)	5	(30)	11
Income (loss) before income tax	422	383	1,127	1,053
Alaska Regional [Member]
Operating revenues
Passenger, Mainline	0	0	0	0
Passenger, Regional	262	249	725	682
Total passenger revenue	262	249	725	682
CPA revenues	0	0	0	0
Freight and mail	1	1	3	3
Other - net revenue	21	21	57	57
Total Operating Revenues	284	271	785	742
Operating expenses
Operating Expenses, Excluding Fuel	219	202	625	580
Economic fuel	45	34	120	90
Total Operating Expenses	264	236	745	670
Nonoperating Income (Expense)
Interest income	0	0	0	0
Interest expense	0	0	0	0
Other	0	0	0	0
Nonoperating Income (Expense) Total	0	0	0	0
Income (loss) before income tax	20	35	40	72
Horizon [Member]
Operating revenues
Passenger, Mainline	0	0	0	0
Passenger, Regional	0	0	0	0
Total passenger revenue	0	0	0	0
CPA revenues	112	109	317	322
Freight and mail	1	0	1	0
Other - net revenue	1	1	3	3
Total Operating Revenues	114	110	321	325
Operating expenses
Operating Expenses, Excluding Fuel	105	99	324	305
Economic fuel	0	0	0	0
Total Operating Expenses	105	99	324	305
Nonoperating Income (Expense)
Interest income	0	0	0	1
Interest expense	(4)	(2)	(9)	(7)
Other	0	0	1	0
Nonoperating Income (Expense) Total	(4)	(2)	(8)	(6)
Income (loss) before income tax	5	9	(11)	14
Intersegment Elimination [Member]
Operating revenues
Passenger, Mainline	0	0	0	0
Passenger, Regional	0	0	0	0
Total passenger revenue	0	0	0	0
CPA revenues	(112)	(109)	(317)	(322)
Freight and mail	0	0	0	0
Other - net revenue	0	1	0	1
Total Operating Revenues	(112)	(108)	(317)	(321)
Operating expenses
Operating Expenses, Excluding Fuel	(112)	(109)	(316)	(322)
Economic fuel	0	0	0	0
Total Operating Expenses	(112)	(109)	(316)	(322)
Nonoperating Income (Expense)
Interest income	(2)	0	(2)	0
Interest expense	1	(2)	0	(3)
Other	0	1	0	4
Nonoperating Income (Expense) Total	(1)	(1)	(2)	1
Income (loss) before income tax	(1)	0	(3)	2
Special Revenue and Charges [Member]
Operating revenues
Passenger, Mainline	0	0	0	0
Passenger, Regional	0	0	0	0
Total passenger revenue	0	0	0	0
CPA revenues	0	0	0	0
Freight and mail	0	0	0	0
Other - net revenue	0	0	0	0
Total Operating Revenues	0	0	0	0
Operating expenses
Operating Expenses, Excluding Fuel	24	22	88	36
Economic fuel	(5)	3	7	(9)
Total Operating Expenses	19	25	95	27
Nonoperating Income (Expense)
Interest income	0	0	0	0
Interest expense	0	0	0	0
Other	0	0	0	0
Nonoperating Income (Expense) Total	0	0	0	0
Income (loss) before income tax	$ (19)	$ (25)	$ (95)	$ (27)