DERIVATIVE INSTRUMENTS - OUTSTANDING FUEL HEDGE POSITIONS (DETAILS) (September 30, 2011 [Member], USD $)	Sep. 30, 2011 Third Quarter 2011 [Member] Swap [Member]	Nov. 03, 2011 Fourth Quarter 2011 [Member] Commodity Option [Member]	Sep. 30, 2011 Fourth Quarter 2011 [Member] Swap [Member]	Nov. 03, 2011 Remainder Of 2011 [Member] Commodity Option [Member]	Nov. 03, 2011 First Quarter 2012 [Member] Commodity Option [Member]	Sep. 30, 2011 First Quarter 2012 [Member] Swap [Member]	Nov. 03, 2011 Second Quarter 2012 [Member] Commodity Option [Member]	Nov. 03, 2011 Third Quarter 2012 [Member] Commodity Option [Member]	Nov. 03, 2011 Fourth Quarter 2012 [Member] Commodity Option [Member]	Nov. 03, 2011 Full Year 2012 [Member] Commodity Option [Member]	Nov. 03, 2011 First Quarter 2013 [Member] Commodity Option [Member]	Nov. 03, 2011 Second Quarter 2013 [Member] Commodity Option [Member]	Nov. 03, 2011 Third Quarter 2013 [Member] Commodity Option [Member]	Nov. 03, 2011 Fourth Quarter 2013 [Member] Commodity Option [Member]	Nov. 03, 2011 Full Year 2013 [Member] Commodity Option [Member]	Nov. 03, 2011 First Quarter 2014 [Member] Commodity Option [Member]	Nov. 03, 2011 Second Quarter 2014 [Member] Commodity Option [Member]	Nov. 03, 2011 Third Quarter 2014 [Member] Commodity Option [Member]	Nov. 03, 2011 Full Year 2014 [Member] Commodity Option [Member]
Derivative [Line Items]
Nonmonetary Notional Amount of Price Risk Derivatives		48,600,000		48,600,000	49,600,000		52,900,000	54,500,000	52,100,000	209,100,000	38,400,000	34,700,000	30,100,000	22,900,000	126,100,000	17,200,000	12,100,000	6,200,000	35,500,000
Derivative, Nonmonetary Notional Amount, Price Per Barrel		$ 86		$ 86	$ 88		$ 92	$ 94	$ 92	$ 92	$ 93	$ 92	$ 93	$ 95	$ 93	$ 96	$ 94	$ 86	$ 94
Derivative Nonmonetary Notional Amount Premium Cost Per Barrel		$ 11		$ 11	$ 12		$ 13	$ 13	$ 13	$ 13	$ 14	$ 15	$ 15	$ 15	$ 14	$ 15	$ 15	$ 16	$ 15
Derivative, Nonmonetary Notional Amount, Percent of Required Need, Coverage	50.00%	50.00%	30.00%	50.00%	50.00%		50.00%	50.00%	50.00%	50.00%	38.00%	32.00%	27.00%	21.00%	29.00%	16.00%	11.00%	5.00%	8.00%
Derivative, Nonmonetary Notional Amount, Estimated Price Per Gallon			0.93			0.92

Derivative Nonmonetary Notional Amount Premium Cost Per Barrel

Name:	alk_DerivativeNonmonetaryNotionalAmountPremiumCostPerBarrel
Namespace Prefix:	alk
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ Details

Name:	us-gaap_DerivativeLineItems
Namespace Prefix:	us-gaap
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage of expected requirements covered by the aggregate notional amount of derivative contracts expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract as a percentage of expected need.

+ Details

Name:	us-gaap_DerivativeNonmonetaryNotionalAmountPercentOfRequiredNeedCoverage
Namespace Prefix:	us-gaap
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The price per barrel of the notional amount of the derivative contract expressed in nonmonetary units. For example, the price per barrel specified in a fuel oil forward purchase contract.

+ Details

Name:	us-gaap_DerivativeNonmonetaryNotionalAmountPricePerBarrel
Namespace Prefix:	us-gaap
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Definition

The price per gallon of the notional amount of the derivative contract expressed in nonmonetary units. For example, the price per gallon specified in a fuel forward purchase contract.

+ Details

Name:	us-gaap_DerivativeNonmonetaryNotionalAmountPricePerGallon
Namespace Prefix:	us-gaap
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Definition

Aggregate notional amount of price risk derivatives for instruments with notional amounts expressed in nonmonetary units.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 1B

-URI http://asc.fasb.org/extlink&oid=6935481&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Notional Amount

-URI http://asc.fasb.org/extlink&oid=6519104

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 1A

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=6935481&loc=SL5579245-113959

+ Details

Name:	us-gaap_NonmonetaryNotionalAmountOfPriceRiskDerivatives
Namespace Prefix:	us-gaap
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant