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Sublease Table (Details) (B-717-200 Aircraft, USD $)
In Millions, unless otherwise specified
 3 Months Ended 12 Months Ended
Mar. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
B-717-200 Aircraft
      
B717 Sublease Liability [Line Items]      
Sublease Obligations $ 48luv_SubleaseObligations
/ us-gaap_AircraftTypeAxis
= us-gaap_B717200Member		 $ 63luv_SubleaseObligations
/ us-gaap_AircraftTypeAxis
= us-gaap_B717200Member		 $ 122luv_SubleaseObligations
/ us-gaap_AircraftTypeAxis
= us-gaap_B717200Member
Interest Expense, Accretion 1luv_InterestExpenseAccretion
/ us-gaap_AircraftTypeAxis
= us-gaap_B717200Member		 5luv_InterestExpenseAccretion
/ us-gaap_AircraftTypeAxis
= us-gaap_B717200Member		  
Additional Estimated Loss on Sublease 4luv_AdditionalEstimatedLossonSublease
/ us-gaap_AircraftTypeAxis
= us-gaap_B717200Member		 22luv_AdditionalEstimatedLossonSublease
/ us-gaap_AircraftTypeAxis
= us-gaap_B717200Member		  
Sublease Transaction Costs $ (20)luv_SubleaseTransactionCosts
/ us-gaap_AircraftTypeAxis
= us-gaap_B717200Member		 [1] $ (86)luv_SubleaseTransactionCosts
/ us-gaap_AircraftTypeAxis
= us-gaap_B717200Member		 [1]  
[1] Includes lease conversion cost payments