COMMITMENTS (DETAILS) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2012 carriers	Mar. 31, 2011
Unrecorded Unconditional Purchase Obligation [Abstract]
Rent Expense	$ 70.0	$ 69.1
Airline, Capacity Purchase Arrangements, Carriers	3
Airline, Capacity Purchase Arrangements, Percent	100.00%
Aircraft Commitments [Member]
Unrecorded Unconditional Purchase Obligation [Abstract]
Remainder of 2012	308.5
2013	307.5
2014	170.4
2015	47.7
2016	18.4
Thereafter	36.8
Total	889.3
Capacity Purchase Agreements[Member]
Unrecorded Unconditional Purchase Obligation [Abstract]
Remainder of 2012	18.8
2013	17.4
2014	17.7
2015	18.0
2016	18.3
Thereafter	26.5
Total	116.7
Engine Maintenance [Member]
Unrecorded Unconditional Purchase Obligation [Abstract]
Remainder of 2012	31.4
2013	31.9
2014	26.4
2015	10.1
2016	0
Thereafter	0
Total	99.8
Aircraft Leases [Member]
Operating Leases, Future Minimum Payments Due [Abstract]
Remainder of 2012	50.5
2013	135.1
2014	125.6
2015	104.4
2016	81.9
Thereafter	130.7
Total	628.2
Unrecorded Unconditional Purchase Obligation [Abstract]
Operating Leases, Number of Units (in Aircraft)	60
Facility Leases [Member]
Operating Leases, Future Minimum Payments Due [Abstract]
Remainder of 2012	46.6
2013	39.9
2014	35.7
2015	24.4
2016	15.7
Thereafter	146.0
Total	$ 308.3
Assets Leased to Others [Member]
Unrecorded Unconditional Purchase Obligation [Abstract]
Operating Leases, Number of Units (in Aircraft)	14
B737-800 [Member]
Unrecorded Unconditional Purchase Obligation [Abstract]
Operating Leases, Number of Units (in Aircraft)	6.0
Commited to Purchase (in Aircraft)	4
B737-900ER [Member]
Unrecorded Unconditional Purchase Obligation [Abstract]
Commited to Purchase (in Aircraft)	19
B737-900ER [Member] \| Options Exercised [Member]
Unrecorded Unconditional Purchase Obligation [Abstract]
Option to Purchase Additional (in Aircraft)	1
B737-900ER [Member] \| Options Intended to be Exercised [Member]
Unrecorded Unconditional Purchase Obligation [Abstract]
Option to Purchase Additional (in Aircraft)	2
B737-900ER [Member] \| Sale Leaseback [Member]
Unrecorded Unconditional Purchase Obligation [Abstract]
Operating Leases, Number of Units (in Aircraft)	3
B737 [Member]
Unrecorded Unconditional Purchase Obligation [Abstract]
Option to Purchase Additional (in Aircraft)	42
Q400 [Member]
Unrecorded Unconditional Purchase Obligation [Abstract]
Commited to Purchase (in Aircraft)	2
Number to be Aircraft Sold	2
Option to Purchase Additional (in Aircraft)	10

Airline, Capacity Purchase Arrangements, Carriers

No definition available.

Name:	alk_AirlineCapacityPurchaseArrangementsCarriers
Namespace Prefix:	alk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Airline, Capacity Purchase Arrangements, Percent

+ References

No definition available.

+ Details

Name:	alk_AirlineCapacityPurchaseArrangementsPercent
Namespace Prefix:	alk_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Number Of Aircraft Sold

+ References

No definition available.

+ Details

Name:	alk_NumberOfAircraftSold
Namespace Prefix:	alk_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Definition

Operating Leases, Number of Units

+ References

No definition available.

+ Details

Name:	alk_OperatingLeasesNumberOfUnits
Namespace Prefix:	alk_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Definition

Unrecorded Unconditional Purchase Obligation, Option to Purchase Additional

+ References

No definition available.

+ Details

Name:	alk_UnrecordedUnconditionalPurchaseObligationOptionToPurchaseAdditional
Namespace Prefix:	alk_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Definition

Rental expense incurred for leased assets including furniture and equipment which has not been recognized in costs and expenses applicable to sales and revenues; for example, cost of goods sold or other operating costs and expenses.

+ References

No definition available.

+ Details

Name:	us-gaap_LeaseAndRentalExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The total of future contractually required payments on leases defined as operating.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 13

-Paragraph 122

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 13

-Paragraph 16

-Subparagraph b(i)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 10

-Section 55

-Paragraph 40

-Subparagraph (Note 3)

-URI http://asc.fasb.org/extlink&oid=6584154&loc=d3e38371-112697

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 20

-Section 50

-Paragraph 2

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6453985&loc=d3e41502-112717

+ Details

Name:	us-gaap_OperatingLeasesFutureMinimumPaymentsDue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_OperatingLeasesFutureMinimumPaymentsDueAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due within one year of the balance sheet date relating to leases defined as operating.

+ References

+ Details

Name:	us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due within the fifth year of the balance sheet date relating to leases defined as operating.

+ References

+ Details

Name:	us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFiveYears
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due within the fourth year of the balance sheet date relating to leases defined as operating.

+ References

+ Details

Name:	us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due within the third year of the balance sheet date relating to leases defined as operating.

+ References

+ Details

Name:	us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due within the second year of the balance sheet date relating to leases defined as operating.

+ References

+ Details

Name:	us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due after the fifth year from the balance sheet date on leases defined as operating.

+ References

+ Details

Name:	us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The remaining amount of the fixed and determinable portion of an unrecorded unconditional purchase obligation to be paid in more than four and within five years from the balance sheet date.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 47

-Paragraph 7

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 440

-SubTopic 10

-Section 50

-Paragraph 4

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6394976&loc=d3e25336-109308

+ Details

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnFifthAnniversary
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The remaining amount of the fixed and determinable portion of an unrecorded unconditional purchase obligation to be paid within one year of the balance sheet date.

+ References

+ Details

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnFirstAnniversary
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The remaining amount of the fixed and determinable portion of an unrecorded unconditional purchase obligation to be paid in more than three and within four years from the balance sheet date.

+ References

+ Details

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnFourthAnniversary
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The remaining amount of the fixed and determinable portion of an unrecorded unconditional purchase obligation to be paid in more than one and within two years from the balance sheet date.

+ References

+ Details

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnSecondAnniversary
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The remaining amount of the fixed and determinable portion of an unrecorded unconditional purchase obligation to be paid in more than two and within three years from the balance sheet date.

+ References

+ Details

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceOnThirdAnniversary
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of the fixed and determinable portion of an unrecorded unconditional purchase obligation as of the balance sheet date.

+ References

+ Details

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationBalanceSheetAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The remaining amount of the fixed and determinable portion of an unrecorded unconditional purchase obligation to be paid after five years from the balance sheet date.

+ References

No definition available.

+ Details

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationDueAfterFiveYears
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The minimum number of units that must be purchased, in connection with an unconditional purchase obligation that has not been recognized for financial reporting purposes.

+ References

No definition available.

+ Details

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationMinimumQuantityRequired
Namespace Prefix:	us-gaap_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant