OPERATING SEGMENT INFORMATION (DETAILS) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010		Dec. 31, 2010
Segment Reporting Information, Profit (Loss) [Abstract]
Passenger Revenue, Mainline	$ 887.4		$ 779.2		$ 2,409.7		$ 2,068.5
Passenger Revenue, Regional	213.4		198.1		584.2		547.0
Passenger Revenue	1,100.8		977.3		2,993.9		2,615.5
Revenue, Net	1,198.1		1,068.0		3,273.5		2,873.8
Operating Expenses	1,054.9		851.1		2,938.7		2,521.5
Nonoperating Income (Expense)	(17.9)		(18.7)		(41.8)		(49.9)
Income before income tax	125.3		198.2		293.0		302.4
Assets	5,260.2				5,260.2				5,016.6
Fleet transition costs	2.0		9.8		38.9		13.2
Alaska Air [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Passenger Revenue, Mainline	887.4	[1]	779.2	[1]	2,409.7	[1]	2,068.5	[1]
Passenger Revenue, Regional	213.4	[1]	88.9	[1]	584.2	[1]	247.6	[1]
Passenger Revenue	1,100.8		868.1		2,993.9		2,316.1
Other revenue and freight and mail revenue	95.3		88.0		273.3		250.1
Revenue, Net	1,196.1		956.1		3,267.2		2,566.2
Operating Expenses	1,060.7		754.6		2,920.3		2,229.3
Nonoperating Income (Expense)	(13.8)		(14.5)		(29.4)		(36.2)
Income before income tax	121.6		187.0		317.5		300.7
Assets	4,845.2				4,845.2				4,610.2
Horizon [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Passenger Revenue, Mainline	0	[2]	109.2	[2]	0	[2]	299.4	[2]
Passenger Revenue, Regional	91.2		69.0		279.3		202.8
Other revenue and freight and mail revenue	2.0		2.7		6.3		8.2
Revenue, Net	93.2		180.9		285.6		510.4
Operating Expenses	84.9	[3]	165.1	[3]	295.8	[3]	492.6	[3]
Nonoperating Income (Expense)	(3.9)	[3]	(4.1)	[3]	(12.1)	[3]	(13.5)	[3]
Income before income tax	4.4	[3]	11.7	[3]	(22.3)	[3]	4.3	[3]
Assets	794.1				794.1				747.2
Capacity Sold Under CPA Percent	100.00%				100.00%
Fleet transition costs	2.0				38.9
Alaska mainline excluding fuel [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating Expenses	504.1		491.8		1,500.2		1,433.5
Alaska mainline fuel [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating Expenses	376.7		188.1		889.2		574.3
Alaska regional [Domain]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating Expenses	179.9		74.7		530.9		221.5
Income before income tax	34.6		14.6		56.6		27.4
Intersegment Elimination [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Revenue, Net	(91.2)		(69.0)		(279.3)		(202.8)
Operating Expenses	(91.2)		(69.0)		(279.3)		(202.8)
Assets									(1,716.4)
Parent Company Results Eliminated In Consolidation [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating Expenses	0.5	[4]	0.4	[4]	1.9	[4]	2.4	[4]
Nonoperating Income (Expense)	(0.2)	[4]	(0.1)	[4]	(0.3)	[4]	(0.2)	[4]
Income before income tax	(0.7)	[4]	(0.5)	[4]	(2.2)	[4]	(2.6)	[4]
Assets	1,595.2	[4]			1,595.2	[4]			1,375.6	[4]
Mainline [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Income before income tax	87.0		172.4		260.9		273.3
CRJ 700 [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Fleet transition costs	$ (2.6)				$ 28.3		$ 10.3

[1] Alaska mainline passenger revenue represents revenue from passengers aboard Alaska jets. Alaska regional passenger revenue represents revenue earned by Alaska on capacity provided by Horizon, SkyWest Airlines and another small third-party carrier in the state of Alaska under capacity purchase arrangements.

[2] As 100% of Horizon's capacity is sold to Alaska under the CPA, Horizon no longer has brand flying revenue.

[3] Includes special charges of $2.0 million and $38.9 million for the three and nine months ended September 30, 2011 related to fleet transition charges at Horizon.

[4] Includes parent company results and its investments in Alaska and Horizon, which are eliminated in consolidation.