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GENERAL AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - LEASE RETURN PROVISION (Details) - USD ($) $ in Millions | Dec. 31, 2021 | Dec. 31, 2020
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Accounting Policies [Abstract] |  |
Lease Return Provision, Current | $ (53) | $ 54
Lease Return Provision, Non-Current | $ (114) | $ 246

X
- Definition Lease Return Provision, Current + References No definition available. + Details
Name: | alk_LeaseReturnProvisionCurrent
Namespace Prefix: | alk_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Lease Return Provision, Non-Current + References No definition available. + Details
Name: | alk_LeaseReturnProvisionNonCurrent
Namespace Prefix: | alk_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_AccountingPoliciesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration