OPERATING SEGMENT INFORMATION (DETAILS) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2011		Jun. 30, 2010		Jun. 30, 2011		Jun. 30, 2010		Dec. 31, 2010
Segment Reporting Information, Profit (Loss) [Abstract]
Passenger Revenue, Mainline	$ 819.9		$ 702.3		$ 1,522.3		$ 1,289.3
Passenger Revenue, Regional	194.3		183.5		370.8		348.9
Passenger Revenue	1,014.2		885.8		1,893.1		1,638.2
Revenue, Net	1,110.2		976.2		2,075.4		1,805.8
Operating Expenses	1,052.4		866.5		1,883.8		1,670.4
Nonoperating Income (Expense)	(10.8)		(15.7)		(23.9)		(31.2)
Income before income tax	47.0		94.0		167.7		104.2
Assets	5,233.8				5,233.8				5,016.6
Fleet transition costs	26.8		3.4		36.9		3.4
Alaska Air [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Passenger Revenue, Mainline	819.9	[1]	702.3	[1]	1,522.3	[1]	1,289.3	[1]
Passenger Revenue, Regional	194.3	[1]	82.6	[1]	370.8	[1]	158.7	[1]
Passenger Revenue	1,014.2		784.9		1,893.1		1,448.0
Other revenue and freight and mail revenue	94.1		87.6		178.0		162.1
Revenue, Net	1,108.3		872.5		2,071.1		1,610.1
Operating Expenses	1,034.0		765.2		1,859.1		1,474.7
Nonoperating Income (Expense)	(6.9)		(10.8)		(15.8)		(21.7)
Income before income tax	67.4		96.5		196.2		113.7
Assets	4,888.3				4,888.3				4,610.2
Horizon [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Passenger Revenue, Mainline	0	[2]	100.9	[2]	0	[2]	190.2	[2]
Passenger Revenue, Regional	93.5		67.4		188.1		133.8
Other revenue and freight and mail revenue	1.9		2.8		4.3		5.5
Revenue, Net	95.4		171.1		192.4		329.5
Operating Expenses	110.6	[3]	167.5	[3]	210.9	[3]	327.5	[3]
Nonoperating Income (Expense)	(4.2)	[3]	(4.8)	[3]	(8.1)	[3]	(9.4)	[3]
Income before income tax	(19.4)	[3]	(1.2)	[3]	(26.6)	[3]	(7.4)	[3]
Assets	816.2				816.2				747.2
Capacity Sold Under CPA Percent	100.00%				100.00%
Fleet transition costs	26.8				36.9
Alaska mainline excluding fuel [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating Expenses	498.4		476.4		996.1		941.7
Alaska mainline fuel [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating Expenses	356.1		214.5		512.5		386.2
Alaska regional [Domain]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating Expenses	179.5		74.3		350.5		146.8
Income before income tax	15.6		8.9		22.3		12.8
Intersegment Elimination [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Revenue, Net	(93.5)		(67.4)		(188.1)		(133.8)
Operating Expenses	(93.5)		(67.4)		(188.1)		(133.8)
Assets	(1,980.2)				(1,980.2)				(1,716.4)
Parent Company Results Eliminated In Consolidation [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Operating Expenses	1.3	[4]	1.2	[4]	1.9	[4]	2.0	[4]
Nonoperating Income (Expense)	0.3	[4]	(0.1)	[4]	0	[4]	(0.1)	[4]
Income before income tax	(1.0)	[4]	(1.3)	[4]	(1.9)	[4]	(2.1)	[4]
Assets	1,509.5	[4]			1,509.5	[4]			1,375.6	[4]
Mainline [Member]
Segment Reporting Information, Profit (Loss) [Abstract]
Income before income tax	$ 51.8		$ 87.6		$ 173.9		$ 100.9

[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 $26.8 million and $36.9 million for the three and six months ended June 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.