OPERATING SEGMENT INFORMATION (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) segment	Sep. 30, 2017 USD ($)
Segment Reporting Information [Line Items]
Number of Operating Segments | segment			3
Operating Revenues
Total Operating Revenues	$ 2,212	$ 2,110	$ 6,200	$ 5,952
Operating expenses
Operating Expenses, Excluding Fuel	1,402	1,315	4,206	3,830
Economic fuel	513	368	1,397	1,051
Total Operating Expenses	1,915	1,683	5,603	4,881
Nonoperating Income (Expense)
Interest income	11	9	29	25
Interest expense	(22)	(26)	(71)	(77)
Interest Costs Capitalized	5	5	14	13
Other	(7)	2	(20)	1
Nonoperating Income (Expense) Total	(13)	(10)	(48)	(38)
Income (loss) before income tax	284	417	549	1,033
Air Group Adjusted [Member]
Operating Revenues
Total Operating Revenues	2,212	2,110	6,200	5,952
Operating expenses
Operating Expenses, Excluding Fuel	1,380	1,292	4,114	3,744
Economic fuel	508	373	1,427	1,044
Total Operating Expenses	1,888	1,665	5,541	4,788
Nonoperating Income (Expense)
Interest income	11	9	29	25
Interest expense	(22)	(26)	(71)	(77)
Interest Costs Capitalized	5	5	14	13
Other	(7)	2	(20)	1
Nonoperating Income (Expense) Total	(13)	(10)	(48)	(38)
Income (loss) before income tax	311	435	611	1,126
Alaska Mainline [Member]
Operating Revenues
Total Operating Revenues	1,884	1,820	5,322	5,147
Operating expenses
Operating Expenses, Excluding Fuel	1,126	1,081	3,392	3,111
Economic fuel	438	328	1,237	924
Total Operating Expenses	1,564	1,409	4,629	4,035
Nonoperating Income (Expense)
Interest income	15	12	39	29
Interest expense	(20)	(25)	(64)	(72)
Interest Costs Capitalized	4	5	12	12
Other	(5)	2	(9)	1
Nonoperating Income (Expense) Total	(6)	(6)	(22)	(30)
Income (loss) before income tax	314	405	671	1,082
Alaska Regional [Member]
Operating Revenues
Total Operating Revenues	326	289	874	802
Operating expenses
Operating Expenses, Excluding Fuel	267	219	755	625
Economic fuel	70	45	190	120
Total Operating Expenses	337	264	945	745
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	(11)	0
Nonoperating Income (Expense) Total	(2)	0	(11)	0
Income (loss) before income tax	(13)	25	(82)	57
Horizon [Member]
Operating Revenues
Total Operating Revenues	130	113	379	320
Operating expenses
Operating Expenses, Excluding Fuel	118	104	345	323
Economic fuel	0	0	0	0
Total Operating Expenses	118	104	345	323
Nonoperating Income (Expense)
Interest income	0	0	0	0
Interest expense	(6)	(4)	(16)	(9)
Interest Costs Capitalized	1	0	2	1
Other	0	0	0	0
Nonoperating Income (Expense) Total	(5)	(4)	(14)	(8)
Income (loss) before income tax	7	5	20	(11)
Intersegment Elimination [Member]
Operating Revenues
Total Operating Revenues	(128)	(112)	(375)	(317)
Operating expenses
Operating Expenses, Excluding Fuel	(131)	(112)	(378)	(315)
Economic fuel	0	0	0	0
Total Operating Expenses	(131)	(112)	(378)	(315)
Nonoperating Income (Expense)
Interest income	(4)	(3)	(10)	(4)
Interest expense	4	3	9	4
Interest Costs Capitalized	0	0	0	0
Other	0	0	0	0
Nonoperating Income (Expense) Total	0	0	(1)	0
Income (loss) before income tax	3	0	2	(2)
Special Revenue and Charges [Member]
Operating Revenues
Total Operating Revenues	0	0	0	0
Operating expenses
Operating Expenses, Excluding Fuel	22	23	92	86
Economic fuel	5	(5)	(30)	7
Total Operating Expenses	27	18	62	93
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	(27)	(18)	(62)	(93)
Passenger [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	2,043	1,958	5,725	5,505
Passenger [Member] | Air Group Adjusted [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	2,043	1,958	5,725	5,505
Passenger [Member] | Alaska Mainline [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	1,727	1,677	4,880	4,729
Passenger [Member] | Alaska Regional [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	316	281	845	776
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	128	112	375	317
Capacity Purchase Agreements [Member] | Intersegment Elimination [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	(128)	(112)	(375)	(317)
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	114	105	329	314
Mileage plan other revenue [Member] | Air Group Adjusted [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	114	105	329	314
Mileage plan other revenue [Member] | Alaska Mainline [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	104	97	301	291
Mileage plan other revenue [Member] | Alaska Regional [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	10	8	28	23
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	55	47	146	133
Cargo and Freight [Member] | Air Group Adjusted [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	55	47	146	133
Cargo and Freight [Member] | Alaska Mainline [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	53	46	141	127
Cargo and Freight [Member] | Alaska Regional [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	0	0	1	3
Cargo and Freight [Member] | Horizon [Member]
Operating Revenues
Revenue from contract with customer, including assessed taxes	2	1	4	3
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