OPERATING SEGMENT INFORMATION (DETAILS) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011
Operating revenues
Mainline	$ 763.7		$ 702.4
Regional	186.7		176.5
Passenger revenues	950.4		878.9
Segment Reporting Information, Intersegment Revenue	0		0
Freight and mail	24.4		24.9
Other - net	64.5		61.4
Total Operating Revenues	1,039.3		965.2
Operating expenses
Operating expenses, excluding fuel	648.1		636.9
Economic fuel	318.8		194.5
Total Operating Expenses	966.9		831.4
Nonoperating income (expense)
Interest income	4.9		7.6
Interest expense	(16.6)		(23.4)
Other	5.9		2.7
Nonoperating Income (Expense) Total	(5.8)		(13.1)
Income (loss) before income tax	66.6		120.7
Air Group Adjusted [Member]
Operating revenues
Mainline	763.7	[1]	702.4	[1]
Regional	186.7	[1]	176.5	[1]
Passenger revenues	950.4	[1]	878.9	[1]
Segment Reporting Information, Intersegment Revenue	0		0
Freight and mail	24.4	[1]	24.9	[1]
Other - net	64.5	[1]	61.4	[1]
Total Operating Revenues	1,039.3	[1]	965.2	[1]
Operating expenses
Operating expenses, excluding fuel	648.1	[1]	626.8	[1]
Economic fuel	338.7	[1]	276.5	[1]
Total Operating Expenses	986.8	[1]	903.3	[1]
Nonoperating income (expense)
Interest income	4.9	[1]	7.6	[1]
Interest expense	(16.6)	[1]	(23.4)	[1]
Other	5.9	[1]	2.7	[1]
Nonoperating Income (Expense) Total	(5.8)	[1]	(13.1)	[1]
Income (loss) before income tax	46.7	[1]	48.8	[1]
Alaska Mainline [Member]
Operating revenues
Mainline	763.7		702.4
Regional	0		0
Passenger revenues	763.7		702.4
Segment Reporting Information, Intersegment Revenue	0		0
Freight and mail	23.5		23.9
Other - net	62.5		59.0
Total Operating Revenues	849.7		785.3
Operating expenses
Operating expenses, excluding fuel	519.6		497.7
Economic fuel	294.4		238.4
Total Operating Expenses	814.0		736.1
Nonoperating income (expense)
Interest income	4.9		8.7
Interest expense	(12.6)		(19.7)
Other	5.3		2.1
Nonoperating Income (Expense) Total	(2.4)		(8.9)
Income (loss) before income tax	33.3		40.3
Alaska Regional [Member]
Operating revenues
Mainline	0		0
Regional	186.7		176.5
Passenger revenues	186.7		176.5
Segment Reporting Information, Intersegment Revenue	0		0
Freight and mail	0.9		1.0
Other - net	0.1		0
Total Operating Revenues	187.7		177.5
Operating expenses
Operating expenses, excluding fuel	136.8		132.9
Economic fuel	44.3		38.1
Total Operating Expenses	181.1		171.0
Nonoperating income (expense)
Interest income	0		0
Interest expense	0		0
Other	0		0
Nonoperating Income (Expense) Total	0		0
Income (loss) before income tax	6.6		6.5
Horizon [Member]
Operating revenues
Mainline	0		0
Regional	0		0
Passenger revenues	0		0
Segment Reporting Information, Intersegment Revenue	87.0		94.6
Freight and mail	0		0
Other - net	1.9		2.4
Total Operating Revenues	88.9		97.0
Operating expenses
Operating expenses, excluding fuel	78.3		90.2
Economic fuel	0		0
Total Operating Expenses	78.3		90.2
Nonoperating income (expense)
Interest income	0		0
Interest expense	(4.0)		(4.7)
Other	0.4		0.8
Nonoperating Income (Expense) Total	(3.6)		(3.9)
Income (loss) before income tax	7.0		2.9
Intersegment Elimination [Member]
Operating revenues
Mainline	0		0
Regional	0		0
Passenger revenues	0		0
Segment Reporting Information, Intersegment Revenue	(87.0)		(94.6)
Freight and mail	0		0
Other - net	0		0
Total Operating Revenues	(87.0)		(94.6)
Operating expenses
Operating expenses, excluding fuel	(86.6)		(94.0)
Economic fuel	0		0
Total Operating Expenses	(86.6)		(94.0)
Nonoperating income (expense)
Interest income	0		(1.1)
Interest expense	0		1.0
Other	0.2		(0.2)
Nonoperating Income (Expense) Total	0.2		(0.3)
Income (loss) before income tax	(0.2)		(0.9)
Special Charges [Member]
Operating revenues
Mainline	0		0
Regional	0		0
Passenger revenues	0		0
Segment Reporting Information, Intersegment Revenue	0		0
Freight and mail	0		0
Other - net	0		0
Total Operating Revenues	0		0
Operating expenses
Operating expenses, excluding fuel	0	[2]	10.1	[2]
Economic fuel	(19.9)	[3]	(82.0)	[3]
Total Operating Expenses	(19.9)		(71.9)
Nonoperating income (expense)
Interest income	0		0
Interest expense	0		0
Other	0		0
Nonoperating Income (Expense) Total	0		0
Income (loss) before income tax	$ 19.9		$ 71.9

[1] The adjusted column represents the financial information that is reviewed by management to assess performance of operations and determine capital allocations and does not include certain charges.

[2] Refer to Note 12 for a summary of special charges.

[3] Represents adjustments to reflect the timing of gain or loss recognition resulting from mark-to-market fuel-hedge accounting.