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GENERAL AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - PROPERTY, EQUIPMENT AND DEPRECIATION (Details) | 12 Months Ended
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Dec. 31, 2015
Buildings [Member] | Maximum [Member] |
Property, Plant and Equipment [Line Items] |
Estimated useful life | 30 years
Buildings [Member] | Minimum [Member] |
Property, Plant and Equipment [Line Items] |
Estimated useful life | 25 years
Minor building and land improvements [Member] |
Property, Plant and Equipment [Line Items] |
Estimated useful life | 10 years
Computer hardware and software [Member] | Maximum [Member] |
Property, Plant and Equipment [Line Items] |
Estimated useful life | 5 years
Computer hardware and software [Member] | Minimum [Member] |
Property, Plant and Equipment [Line Items] |
Estimated useful life | 3 years
Other furniture and equipment [Member] | Maximum [Member] |
Property, Plant and Equipment [Line Items] |
Estimated useful life | 10 years
Other furniture and equipment [Member] | Minimum [Member] |
Property, Plant and Equipment [Line Items] |
Estimated useful life | 5 years
B737 | Aircraft [Member] |
Property, Plant and Equipment [Line Items] |
Estimated useful life | 20 years
Q400 [Member] | Aircraft [Member] |
Property, Plant and Equipment [Line Items] |
Estimated useful life | 15 years

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

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- Definition Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_BuildingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

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

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- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=alk_MinorBuildingAndLandImprovementsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_TechnologyEquipmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_OfficeEquipmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_AircraftTypeAxis=us-gaap_B737Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=alk_AircraftMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_AircraftTypeAxis=alk_Q400Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |