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Supplemental Financial Information - Narrative (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2017 | Sep. 30, 2016 | Sep. 30, 2017 | Sep. 30, 2016
Supplemental Financial Information Narrative [Abstract] |  |  |  |
Aircraft Grounding Charge Prepaid Rent | $ 15 |  | $ 15 |
Aircraft grounding charge | $ 63 | $ 0 | $ 63 | $ 0

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- Definition Aircraft Grounding Charge Prepaid Rent + References No definition available. + Details
Name: | luv_AircraftGroundingChargePrepaidRent
Namespace Prefix: | luv_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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- Definition Aircraft grounding charge + References No definition available. + Details
Name: | luv_Aircraftgroundingcharge
Namespace Prefix: | luv_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Supplemental Financial Information Narrative [Abstract] + References No definition available. + Details
Name: | luv_SupplementalFinancialInformationNarrativeAbstract
Namespace Prefix: | luv_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration