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LEASES Sublease Table (Details) (B-717-200, USD $)
In Millions, unless otherwise specified
 3 Months Ended 12 Months Ended
Jun. 30, 2014
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
B-717-200
        
B717 Sublease Liability [Line Items]        
Sublease Obligations   $ 63luv_SubleaseObligations
/ us-gaap_AircraftTypeAxis
= us-gaap_B717200Member		 $ 122luv_SubleaseObligations
/ us-gaap_AircraftTypeAxis
= us-gaap_B717200Member		 $ 128luv_SubleaseObligations
/ us-gaap_AircraftTypeAxis
= us-gaap_B717200Member
Interest Expense, Accretion   5luv_InterestExpenseAccretion
/ us-gaap_AircraftTypeAxis
= us-gaap_B717200Member		 6luv_InterestExpenseAccretion
/ us-gaap_AircraftTypeAxis
= us-gaap_B717200Member		  
Sublease Transaction Costs   (86)luv_SubleaseTransactionCosts
/ us-gaap_AircraftTypeAxis
= us-gaap_B717200Member		 [1] (12)luv_SubleaseTransactionCosts
/ us-gaap_AircraftTypeAxis
= us-gaap_B717200Member		 [1]  
Additional Estimated Loss on Sublease $ 22luv_AdditionalEstimatedLossonSublease
/ us-gaap_AircraftTypeAxis
= us-gaap_B717200Member		 $ 22luv_AdditionalEstimatedLossonSublease
/ us-gaap_AircraftTypeAxis
= us-gaap_B717200Member		    
[1] Includes lease conversion cost payments