OPERATING SEGMENT INFORMATION (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018 USD ($) segment	Mar. 31, 2017 USD ($)
Segment Reporting Information [Line Items]
Number of Operating Segments | segment	3
Operating Revenues
Passenger revenue	$ 1,685	$ 1,602
CPA revenues	0	0
Mileage plan other revenue	107	100
Cargo and other	40	38
Total Operating Revenues	1,832	1,740
Operating expenses
Operating Expenses, Excluding Fuel	1,394	1,244
Economic fuel	409	339
Total Operating Expenses	1,803	1,583
Nonoperating Income (Expense)
Interest income	8	7
Interest expense	(24)	(25)
Interest Costs Capitalized	5	4
Other	(12)	(1)
Nonoperating Income (Expense) Total	(23)	(15)
Income (loss) before income tax	6	142
Air Group Adjusted [Member]
Operating Revenues
Passenger revenue	1,685	1,602
CPA revenues	0	0
Mileage plan other revenue	107	100
Cargo and other	40	38
Total Operating Revenues	1,832	1,740
Operating expenses
Operating Expenses, Excluding Fuel	1,363	1,205
Economic fuel	422	329
Total Operating Expenses	1,785	1,534
Nonoperating Income (Expense)
Interest income	8	7
Interest expense	(24)	(25)
Interest Costs Capitalized	5	4
Other	(12)	(1)
Nonoperating Income (Expense) Total	(23)	(15)
Income (loss) before income tax	24	191
Alaska Mainline [Member]
Operating Revenues
Passenger revenue	1,442	1,375
CPA revenues	0	0
Mileage plan other revenue	98	93
Cargo and other	39	36
Total Operating Revenues	1,579	1,504
Operating expenses
Operating Expenses, Excluding Fuel	1,131	1,000
Economic fuel	367	292
Total Operating Expenses	1,498	1,292
Nonoperating Income (Expense)
Interest income	11	7
Interest expense	(22)	(23)
Interest Costs Capitalized	4	4
Other	(5)	(1)
Nonoperating Income (Expense) Total	(12)	(13)
Income (loss) before income tax	69	199
Alaska Regional [Member]
Operating Revenues
Passenger revenue	243	227
CPA revenues	0	0
Mileage plan other revenue	9	7
Cargo and other	0	1
Total Operating Revenues	252	235
Operating expenses
Operating Expenses, Excluding Fuel	239	200
Economic fuel	55	37
Total Operating Expenses	294	237
Nonoperating Income (Expense)
Interest income	0	0
Interest expense	0	0
Interest Costs Capitalized	0	0
Other	(7)	0
Nonoperating Income (Expense) Total	(7)	0
Income (loss) before income tax	(49)	(2)
Horizon [Member]
Operating Revenues
Passenger revenue	0	0
CPA revenues	110	97
Mileage plan other revenue	0	0
Cargo and other	1	1
Total Operating Revenues	111	98
Operating expenses
Operating Expenses, Excluding Fuel	104	103
Economic fuel	0	0
Total Operating Expenses	104	103
Nonoperating Income (Expense)
Interest income	0	0
Interest expense	(5)	(2)
Interest Costs Capitalized	1	0
Other	0	0
Nonoperating Income (Expense) Total	(4)	(2)
Income (loss) before income tax	3	(7)
Intersegment Elimination [Member]
Operating Revenues
Passenger revenue	0	0
CPA revenues	(110)	(97)
Mileage plan other revenue	0	0
Cargo and other	0	0
Total Operating Revenues	(110)	(97)
Operating expenses
Operating Expenses, Excluding Fuel	(111)	(98)
Economic fuel	0	0
Total Operating Expenses	(111)	(98)
Nonoperating Income (Expense)
Interest income	(3)	0
Interest expense	3	0
Interest Costs Capitalized	0	0
Other	0	0
Nonoperating Income (Expense) Total	0	0
Income (loss) before income tax	1	1
Special Revenue and Charges [Member]
Operating Revenues
Passenger revenue	0	0
CPA revenues	0	0
Mileage plan other revenue	0	0
Cargo and other	0	0
Total Operating Revenues	0	0
Operating expenses
Operating Expenses, Excluding Fuel	31	39
Economic fuel	(13)	10
Total Operating Expenses	18	49
Nonoperating Income (Expense)
Interest income	0	0
Interest expense	0	0
Interest Costs Capitalized	0	0
Other	0	0
Nonoperating Income (Expense) Total	0	0
Income (loss) before income tax	$ (18)	$ (49)