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Revenue - Air Traffic Liability Rollforward (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2018 | Dec. 31, 2017
Air Traffic Liability Rollforward [Abstract] |  |
ATL, beginning balance | $ 4,565 | $ 4,221
Current Period Sales | 21,026 | 20,146
Revenue amounts in beginning balance | (3,479) | (3,099)
Revenue from Current Period Sales | (17,042) | (16,703)
ATL, ending balance | $ 5,070 | $ 4,565

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- Definition Current Period Sales + References No definition available. + Details
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Namespace Prefix: | luv_
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Balance Type: | credit
Period Type: | duration

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- Definition Air Traffic Liability - Revenue amounts in beginning balance + References No definition available. + Details
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- Definition Air Traffic Liability - Revenue from Current Period Sales + References No definition available. + Details
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Namespace Prefix: | luv_
Data Type: | xbrli:monetaryItemType
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- Definition Air Traffic Liability Rollforward + References No definition available. + Details
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Namespace Prefix: | luv_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Air Traffic Liability Total + References No definition available. + Details
Name: | luv_AirTrafficLiabilityTotal
Namespace Prefix: | luv_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant