OPERATING SEGMENT INFORMATION (Details) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) segment	Jun. 30, 2017 USD ($)
Segment Reporting Information [Line Items]
Number of Operating Segments | segment			3
Operating Revenues
Total Operating Revenues	$ 2,156	$ 2,102	$ 3,988	$ 3,842
Operating expenses
Operating Expenses, Excluding Fuel	1,410	1,271	2,804	2,515
Economic fuel	475	344	884	683
Total Operating Expenses	1,885	1,615	3,688	3,198
Nonoperating Income (Expense)
Interest income	10	9	18	16
Interest expense	(25)	(26)	(49)	(51)
Interest Costs Capitalized	4	4	9	8
Other	(1)	0	(13)	(1)
Nonoperating Income (Expense) Total	(12)	(13)	(35)	(28)
Income (loss) before income tax	259	474	265	616
Air Group Adjusted [Member]
Operating Revenues
Total Operating Revenues	2,156	2,102	3,988	3,842
Operating expenses
Operating Expenses, Excluding Fuel	1,371	1,247	2,734	2,452
Economic fuel	497	342	919	671
Total Operating Expenses	1,868	1,589	3,653	3,123
Nonoperating Income (Expense)
Interest income	10	9	18	16
Interest expense	(25)	(26)	(49)	(51)
Interest Costs Capitalized	4	4	9	8
Other	(1)	0	(13)	(1)
Nonoperating Income (Expense) Total	(12)	(13)	(35)	(28)
Income (loss) before income tax	276	500	300	691
Alaska Mainline [Member]
Operating Revenues
Total Operating Revenues	1,859	1,823	3,438	3,327
Operating expenses
Operating Expenses, Excluding Fuel	1,135	1,030	2,266	2,030
Economic fuel	432	304	799	596
Total Operating Expenses	1,567	1,334	3,065	2,626
Nonoperating Income (Expense)
Interest income	13	10	24	17
Interest expense	(22)	(24)	(44)	(47)
Interest Costs Capitalized	4	3	8	7
Other	1	0	(4)	(1)
Nonoperating Income (Expense) Total	(4)	(11)	(16)	(24)
Income (loss) before income tax	288	478	357	677
Alaska Regional [Member]
Operating Revenues
Total Operating Revenues	296	278	548	513
Operating expenses
Operating Expenses, Excluding Fuel	249	206	488	406
Economic fuel	65	38	120	75
Total Operating Expenses	314	244	608	481
Nonoperating Income (Expense)
Interest income	0	0	0	0
Interest expense	0	0	0	0
Interest Costs Capitalized	0	0	0	0
Other	(2)	0	(9)	0
Nonoperating Income (Expense) Total	(2)	0	(9)	0
Income (loss) before income tax	(20)	34	(69)	32
Horizon [Member]
Operating Revenues
Total Operating Revenues	138	109	249	207
Operating expenses
Operating Expenses, Excluding Fuel	123	116	227	219
Economic fuel	0	0	0	0
Total Operating Expenses	123	116	227	219
Nonoperating Income (Expense)
Interest income	0	0	0	0
Interest expense	(5)	(3)	(10)	(5)
Interest Costs Capitalized	0	1	1	1
Other	0	0	0	0
Nonoperating Income (Expense) Total	(5)	(2)	(9)	(4)
Income (loss) before income tax	10	(9)	13	(16)
Intersegment Elimination [Member]
Operating Revenues
Total Operating Revenues	(137)	(108)	(247)	(205)
Operating expenses
Operating Expenses, Excluding Fuel	(136)	(105)	(247)	(203)
Economic fuel	0	0	0	0
Total Operating Expenses	(136)	(105)	(247)	(203)
Nonoperating Income (Expense)
Interest income	(3)	(1)	(6)	(1)
Interest expense	2	1	5	1
Interest Costs Capitalized	0	0	0	0
Other	0	0	0	0
Nonoperating Income (Expense) Total	(1)	0	(1)	0
Income (loss) before income tax	(2)	(3)	(1)	(2)
Special Revenue and Charges [Member]
Operating Revenues
Total Operating Revenues	0	0	0	0
Operating expenses
Operating Expenses, Excluding Fuel	39	24	70	63
Economic fuel	(22)	2	(35)	12
Total Operating Expenses	17	26	35	75
Nonoperating Income (Expense)
Interest income	0	0	0	0
Interest expense	0	0	0	0
Interest Costs Capitalized	0	0	0	0
Other	0	0	0	0
Nonoperating Income (Expense) Total	0	0	0	0
Income (loss) before income tax	(17)	(26)	(35)	(75)
Passenger [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	1,997	1,945	3,682	3,547
Passenger [Member] | Air Group Adjusted [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	1,997	1,945	3,682	3,547
Passenger [Member] | Alaska Mainline [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	1,711	1,677	3,153	3,052
Passenger [Member] | Alaska Regional [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	286	268	529	495
Passenger [Member] | Horizon [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0	0	0
Passenger [Member] | Intersegment Elimination [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0	0	0
Passenger [Member] | Special Revenue and Charges [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0	0	0
Capacity Purchase Agreements [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0	0	0
Capacity Purchase Agreements [Member] | Air Group Adjusted [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0	0	0
Capacity Purchase Agreements [Member] | Alaska Mainline [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0	0	0
Capacity Purchase Agreements [Member] | Alaska Regional [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0	0	0
Capacity Purchase Agreements [Member] | Horizon [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	137	108	247	205
Capacity Purchase Agreements [Member] | Intersegment Elimination [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	(137)	(108)	(247)	(205)
Capacity Purchase Agreements [Member] | Special Revenue and Charges [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0	0	0
Mileage plan other revenue [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	108	109	215	209
Mileage plan other revenue [Member] | Air Group Adjusted [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	108	109	215	209
Mileage plan other revenue [Member] | Alaska Mainline [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	99	101	197	194
Mileage plan other revenue [Member] | Alaska Regional [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	9	8	18	15
Mileage plan other revenue [Member] | Horizon [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0	0	0
Mileage plan other revenue [Member] | Intersegment Elimination [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0	0	0
Mileage plan other revenue [Member] | Special Revenue and Charges [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0	0	0
Cargo and Freight [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	51	48	91	86
Cargo and Freight [Member] | Air Group Adjusted [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	51	48	91	86
Cargo and Freight [Member] | Alaska Mainline [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	49	45	88	81
Cargo and Freight [Member] | Alaska Regional [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	1	2	1	3
Cargo and Freight [Member] | Horizon [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	1	1	2	2
Cargo and Freight [Member] | Intersegment Elimination [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0	0	0
Cargo and Freight [Member] | Special Revenue and Charges [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	$ 0	$ 0	$ 0	$ 0