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v3.20.4

SPECIAL ITEMS Other Special Items (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Other Special Items [Line Items] |  |  |
Special items—other | $ 0 | $ 0 | $ 45
Settlement Fee [Member] |  |  |
Other Special Items [Line Items] |  |  |
Special items—other | 20 |  |
One-time Bonus Payment [Member] |  |  |
Other Special Items [Line Items] |  |  |
Special items—other | $ 25 |  |

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- Definition [Line Items] for Other Special Items [Table] + References No definition available. + Details
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Namespace Prefix: | alk_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Special items—other + References No definition available. + Details
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Namespace Prefix: | alk_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |