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v3.20.4

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