OPERATING SEGMENT INFORMATION (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017		Dec. 31, 2016
Operating revenues
Total Operating Revenues		$ 8,264	$ 7,894		$ 5,925
Operating expenses
Operating expenses, excluding fuel		5,685	5,239		3,788
Special items - merger-related costs		87	116		117
Economic fuel		1,936	1,447		831
Total Operating Expenses		7,621	6,686		4,619
Nonoperating Income (Expense)
Interest income		38	34		27
Interest expense		(91)	(103)		(55)
Interest capitalized		18	17		25
Other—net		(23)	3		13
Nonoperating Income (Expense) Total		(58)	(49)		10
Income (loss) before income tax		585	1,159		1,316
Depreciation		398	372		363
Total property and equipment additions		(960)	(1,026)		(678)
Total assets		10,912	10,746
Air Group Adjusted [Member]
Operating revenues
Total Operating Revenues	[1]	8,264	7,894		5,925
Operating expenses
Operating expenses, excluding fuel	[1]	5,553	5,123		3,671
Economic fuel	[1]	1,914	1,454		844
Total Operating Expenses	[1]	7,467	6,577		4,515
Nonoperating Income (Expense)
Interest income		38	34		27
Interest expense		(91)	(103)		(55)
Interest capitalized		18	17		25
Other—net		(23)	3		13
Nonoperating Income (Expense) Total	[1]	(58)	(49)		10
Income (loss) before income tax	[1]	739	1,268		1,420
Alaska Mainline [Member]
Operating revenues
Total Operating Revenues		7,063	6,832		4,908
Operating expenses
Operating expenses, excluding fuel		4,577	4,271		2,919
Economic fuel		1,652	1,282		719
Total Operating Expenses		6,229	5,553		3,638
Nonoperating Income (Expense)
Interest income		53	39		26
Interest expense		(82)	(92)		(42)
Interest capitalized		16	15		20
Other—net		(12)	3		13
Nonoperating Income (Expense) Total		(25)	(35)		17
Income (loss) before income tax		809	1,244		1,287
Depreciation	[2]	316	308		296
Total property and equipment additions	[2]	(571)	(734)		(608)
Total assets	[2]	16,853	16,663
Alaska Regional [Member]
Operating revenues
Total Operating Revenues		1,197	1,058		1,018
Operating expenses
Operating expenses, excluding fuel		1,024	852		769
Economic fuel		262	172		125
Total Operating Expenses		1,286	1,024		894
Nonoperating Income (Expense)
Interest income		0	0		0
Interest expense		0	0		0
Interest capitalized		0	0		0
Other—net		(11)	0		0
Nonoperating Income (Expense) Total		(11)	0		0
Income (loss) before income tax		(100)	34		124
Horizon [Member]
Operating revenues
Total Operating Revenues		512	430		424
Operating expenses
Operating expenses, excluding fuel		465	427		407
Economic fuel		0	0		0
Total Operating Expenses		465	427		407
Nonoperating Income (Expense)
Interest income		0	0		1
Interest expense		(22)	(13)		(9)
Interest capitalized		2	2		1
Other—net		0	0		0
Nonoperating Income (Expense) Total		(20)	(11)		(7)
Income (loss) before income tax		27	(8)		10
Depreciation		82	64		67
Total property and equipment additions		(389)	(292)		(70)
Total assets		1,229	929
Parent [Member]
Nonoperating Income (Expense)
Total assets		(7,170)	(6,846)
Intersegment Eliminations
Operating revenues
Total Operating Revenues		(508)	(426)		(425)
Operating expenses
Operating expenses, excluding fuel		(513)	(427)		(424)
Economic fuel		0	0		0
Total Operating Expenses		(513)	(427)		(424)
Nonoperating Income (Expense)
Interest income		(15)	(5)		0
Interest expense		13	2		(4)
Interest capitalized		0	0		4
Other—net		0	0		0
Nonoperating Income (Expense) Total		(2)	(3)		0
Income (loss) before income tax		3	(2)		(1)
Special Charges [Member]
Operating revenues
Total Operating Revenues	[3]	0	0		0
Operating expenses
Operating expenses, excluding fuel		132	116	[3]	117	[3]
Economic fuel		22	(7)	[3]	(13)	[3]
Total Operating Expenses	[3]	154	109		104
Nonoperating Income (Expense)
Interest income		0	0		0
Interest expense		0	0		0
Interest capitalized		0	0		0
Other—net		0	0		0
Nonoperating Income (Expense) Total	[3]	0	0		0
Income (loss) before income tax	[3]	(154)	(109)		(104)
Passenger Revenue [Member]
Operating revenues
Revenue from Contract with Customer, Excluding Assessed Tax		7,632	7,301		5,392
Passenger Revenue [Member] | Air Group Adjusted [Member]
Operating revenues
Revenue from Contract with Customer, Excluding Assessed Tax	[1]	7,632	7,301		5,392
Passenger Revenue [Member] | Alaska Mainline [Member]
Operating revenues
Revenue from Contract with Customer, Excluding Assessed Tax		6,475	6,278		4,415
Passenger Revenue [Member] | Alaska Regional [Member]
Operating revenues
Revenue from Contract with Customer, Excluding Assessed Tax		1,157	1,023		977
Passenger Revenue [Member] | Horizon [Member]
Operating revenues
Revenue from Contract with Customer, Excluding Assessed Tax		0	0		0
Passenger Revenue [Member] | Intersegment Eliminations
Operating revenues
Revenue from Contract with Customer, Excluding Assessed Tax		0	0		0
Passenger Revenue [Member] | Special Charges [Member]
Operating revenues
Revenue from Contract with Customer, Excluding Assessed Tax	[3]	0	0		0
Capacity Purchase Agreements [Member]
Operating revenues
Revenue from Contract with Customer, Excluding Assessed Tax		0	0		0
Capacity Purchase Agreements [Member] | Air Group Adjusted [Member]
Operating revenues
Revenue from Contract with Customer, Excluding Assessed Tax	[1]	0	0		0
Capacity Purchase Agreements [Member] | Alaska Mainline [Member]
Operating revenues
Revenue from Contract with Customer, Excluding Assessed Tax		0	0		0
Capacity Purchase Agreements [Member] | Alaska Regional [Member]
Operating revenues
Revenue from Contract with Customer, Excluding Assessed Tax		0	0		0
Capacity Purchase Agreements [Member] | Horizon [Member]
Operating revenues
Revenue from Contract with Customer, Excluding Assessed Tax		508	426		424
Capacity Purchase Agreements [Member] | Intersegment Eliminations
Operating revenues
Revenue from Contract with Customer, Excluding Assessed Tax		(508)	(426)		(424)
Capacity Purchase Agreements [Member] | Special Charges [Member]
Operating revenues
Revenue from Contract with Customer, Excluding Assessed Tax	[3]	0	0		0
Mileage Plan Services, Other [Member]
Operating revenues
Revenue from Contract with Customer, Excluding Assessed Tax		434	418		370
Mileage Plan Services, Other [Member] | Air Group Adjusted [Member]
Operating revenues
Revenue from Contract with Customer, Excluding Assessed Tax	[1]	434	418		370
Mileage Plan Services, Other [Member] | Alaska Mainline [Member]
Operating revenues
Revenue from Contract with Customer, Excluding Assessed Tax		397	387		333
Mileage Plan Services, Other [Member] | Alaska Regional [Member]
Operating revenues
Revenue from Contract with Customer, Excluding Assessed Tax		37	31		37
Mileage Plan Services, Other [Member] | Horizon [Member]
Operating revenues
Revenue from Contract with Customer, Excluding Assessed Tax		0	0		0
Mileage Plan Services, Other [Member] | Intersegment Eliminations
Operating revenues
Revenue from Contract with Customer, Excluding Assessed Tax		0	0		0
Mileage Plan Services, Other [Member] | Special Charges [Member]
Operating revenues
Revenue from Contract with Customer, Excluding Assessed Tax	[3]	0	0		0
Cargo and Freight [Member]
Operating revenues
Revenue from Contract with Customer, Excluding Assessed Tax		198	175		163
Cargo and Freight [Member] | Air Group Adjusted [Member]
Operating revenues
Revenue from Contract with Customer, Excluding Assessed Tax	[1]	198	175		163
Cargo and Freight [Member] | Alaska Mainline [Member]
Operating revenues
Revenue from Contract with Customer, Excluding Assessed Tax		191	167		160
Cargo and Freight [Member] | Alaska Regional [Member]
Operating revenues
Revenue from Contract with Customer, Excluding Assessed Tax		3	4		4
Cargo and Freight [Member] | Horizon [Member]
Operating revenues
Revenue from Contract with Customer, Excluding Assessed Tax		4	4		0
Cargo and Freight [Member] | Intersegment Eliminations
Operating revenues
Revenue from Contract with Customer, Excluding Assessed Tax		0	0		(1)
Cargo and Freight [Member] | Special Charges [Member]
Operating revenues
Revenue from Contract with Customer, Excluding Assessed Tax	[3]	$ 0	$ 0		$ 0

[1] Year Ended December 31, 2016 Mainline(a) Regional Horizon Consolidating & Other(b) Air Group Adjusted(c) Special Items(d) ConsolidatedOperating revenues Passenger revenues4,415 977 — — 5,392 — 5,392CPA revenues— — 424 (424) — — —Mileage Plan other revenue333 37 — — 370 — 370Cargo and other160 4 — (1) 163 — 163Total operating revenues4,908 1,018 424 (425) 5,925 — 5,925Operating expenses Non-fuel operating expenses2,919 769 407 (424) 3,671 117 3,788Fuel expense719 125 — — 844 (13) 831Total operating expenses3,638 894 407 (424) 4,515 104 4,619Nonoperating income (expense) Interest income26 — 1 — 27 — 27Interest expense(42) — (9) (4) (55) — (55)Interest capitalized20 — 1 4 25 — 25Other13 — — — 13 — 13Total nonoperating income (expense)17 — (7) — 10 — 10Income (loss) before income tax$1,287 $124 $10 $(1) $1,420 $(104) $1,316

[2] 2018 2017 2016Depreciation and amortization: Mainline$316 $308 $296Horizon82 64 67Consolidated$398 $372 $363 Capital expenditures: Mainline$571 $734 $608Horizon389 292 70Consolidated$960 $1,026 $678 Total assets at end of period: Mainline$16,853 $16,663 Horizon1,229 929 Consolidating & Other(7,170) (6,846) Consolidated$10,912 $10,746

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