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GENERAL AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - NARRATIVE (Details) - Accounting Standards Update 2014-09 [Member] - Scenario, Forecast [Member] $ in Millions | Jan. 01, 2018 USD ($)
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Minimum [Member] |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |
Contract with Customer, Liability | $ 350
Maximum [Member] |
New Accounting Pronouncements or Change in Accounting Principle [Line Items] |
Contract with Customer, Liability | $ 450

X
- Definition Contract with Customer, Liability + References No definition available. + Details
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Namespace Prefix: | alk_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=us-gaap_AccountingStandardsUpdate201409Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementScenarioAxis=us-gaap_ScenarioForecastMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |