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Summary of Significant Accounting Policies (Details) (USD $)
 12 Months Ended 3 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2012
Dec. 31, 2014
Accounting Policies [Abstract]          
Prior Period Reclassification Adjustment   $ (14,000,000)us-gaap_PriorPeriodReclassificationAdjustment      
Inventory reserve for obsolescence 46,000,000us-gaap_InventoryValuationReserves 36,000,000us-gaap_InventoryValuationReserves     46,000,000us-gaap_InventoryValuationReserves
The percentage of the amount received per flight segment sold that relate to free travel-SWA (in hundredths) 100.00%luv_FundsRelatedToFreeTravelPercentageSW        
Frequent flyer points and flight credits liability 1,300,000,000us-gaap_FrequentFlierLiabilityCurrent 1,100,000,000us-gaap_FrequentFlierLiabilityCurrent     1,300,000,000us-gaap_FrequentFlierLiabilityCurrent
Capitalized computer software, net 403,000,000us-gaap_CapitalizedComputerSoftwareNet 357,000,000us-gaap_CapitalizedComputerSoftwareNet     403,000,000us-gaap_CapitalizedComputerSoftwareNet
Computer software depreciation expense 122,000,000us-gaap_CapitalizedComputerSoftwareAmortization 90,000,000us-gaap_CapitalizedComputerSoftwareAmortization 59,000,000us-gaap_CapitalizedComputerSoftwareAmortization    
Advertising costs 207,000,000us-gaap_AdvertisingExpense 208,000,000us-gaap_AdvertisingExpense 223,000,000us-gaap_AdvertisingExpense    
Concentration Risk [Line Items]          
The percentage of employees subject to amendable agreements in the current year (in hundredths) 70.00%luv_PercentageOfEmployeesSubjectToAmendableAgreementsInCurrentYear       70.00%luv_PercentageOfEmployeesSubjectToAmendableAgreementsInCurrentYear
Acquired Finite-Lived Intangible Assets [Line Items]          
Gross carrying amount (in millions) (a) 461,000,000luv_IntangibleAssetsGross 252,000,000luv_IntangibleAssetsGross     461,000,000luv_IntangibleAssetsGross
Weighted-average useful life (in years) 15 years        
Accumulated amortization (in millions) (a) 98,000,000us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization 86,000,000us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization     98,000,000us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
Amortization of intangible assets 13,000,000us-gaap_AmortizationOfIntangibleAssets 19,000,000us-gaap_AmortizationOfIntangibleAssets 25,000,000us-gaap_AmortizationOfIntangibleAssets    
Finite-Lived Intangible Assets, Future Amortization Expense [Abstract]          
2015 11,000,000us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths       11,000,000us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths
2016 8,000,000us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo       8,000,000us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo
2017 5,000,000us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree       5,000,000us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree
2018 5,000,000us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour       5,000,000us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour
2019 4,000,000us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFive       4,000,000us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFive
Thereafter 27,000,000us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFive       27,000,000us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFive
Customer relationships/marketing agreements          
Acquired Finite-Lived Intangible Assets [Line Items]          
Gross carrying amount of finite-lived intangible assets 38,000,000us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_CustomerRelationshipsMember		 39,000,000us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_CustomerRelationshipsMember		     38,000,000us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_CustomerRelationshipsMember
Weighted-average useful life (in years) 9 years        
Accumulated amortization (in millions) (a) 26,000,000us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_CustomerRelationshipsMember		 23,000,000us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_CustomerRelationshipsMember		     26,000,000us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_CustomerRelationshipsMember
Trademarks/trade names          
Acquired Finite-Lived Intangible Assets [Line Items]          
Gross carrying amount of finite-lived intangible assets 36,000,000us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_TrademarksMember		 36,000,000us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_TrademarksMember		     36,000,000us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_TrademarksMember
Weighted-average useful life (in years) 6 years        
Accumulated amortization (in millions) (a) 30,000,000us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_TrademarksMember		 25,000,000us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_TrademarksMember		     30,000,000us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_TrademarksMember
Owned domestic slots          
Acquired Finite-Lived Intangible Assets [Line Items]          
Gross carrying amount of indefinite-lived intangible assets 303,000,000us-gaap_IndefiniteLivedDomesticSlotsAndRoutes
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_UseRightsMember		 93,000,000us-gaap_IndefiniteLivedDomesticSlotsAndRoutes
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_UseRightsMember		     303,000,000us-gaap_IndefiniteLivedDomesticSlotsAndRoutes
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_UseRightsMember
Contract-Based Intangible Assets [Member]          
Acquired Finite-Lived Intangible Assets [Line Items]          
Gross carrying amount of finite-lived intangible assets 19,000,000us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_ContractBasedIntangibleAssetsMember		 [1] 19,000,000us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_ContractBasedIntangibleAssetsMember		 [1]     19,000,000us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_ContractBasedIntangibleAssetsMember		 [1]
Weighted-average useful life (in years) 39 years [1]        
Accumulated amortization (in millions) (a) 5,000,000us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_ContractBasedIntangibleAssetsMember		 [1] 4,000,000us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_ContractBasedIntangibleAssetsMember		 [1]     5,000,000us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_ContractBasedIntangibleAssetsMember		 [1]
Non-compete agreements          
Acquired Finite-Lived Intangible Assets [Line Items]          
Gross carrying amount of finite-lived intangible assets 5,000,000us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_NoncompeteAgreementsMember		 5,000,000us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_NoncompeteAgreementsMember		     5,000,000us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_NoncompeteAgreementsMember
Weighted-average useful life (in years) 2 years        
Accumulated amortization (in millions) (a) 5,000,000us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_NoncompeteAgreementsMember		 5,000,000us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_NoncompeteAgreementsMember		     5,000,000us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_NoncompeteAgreementsMember
Gate leasehold rights          
Acquired Finite-Lived Intangible Assets [Line Items]          
Gross carrying amount of finite-lived intangible assets 60,000,000us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_LeaseAgreementsMember		 60,000,000us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_LeaseAgreementsMember		     60,000,000us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_LeaseAgreementsMember
Weighted-average useful life (in years) 19 years        
Accumulated amortization (in millions) (a) 32,000,000us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_LeaseAgreementsMember		 29,000,000us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_LeaseAgreementsMember		     32,000,000us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_LeaseAgreementsMember
Flight equipment          
Property, Plant and Equipment [Line Items]          
Minimum percentage of cost estimated residual value (in hundredths) 2.00%luv_PropertyPlantAndEquipmentPercentageCostToResidualValueMinimum
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_FlightEquipmentMember		        
Maximum percentage of cost estimated as residual value (in hundredths) 20.00%luv_PropertyPlantAndEquipmentPercentageCostToResidualValueMaximum
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_FlightEquipmentMember		        
Flight equipment | Minimum          
Property, Plant and Equipment [Line Items]          
Property, Plant, and Equipment Useful Life 23 years        
Flight equipment | Maximum          
Property, Plant and Equipment [Line Items]          
Property, Plant, and Equipment Useful Life 25 years        
Property, Plant and Equipment [Member] | Minimum          
Property, Plant and Equipment [Line Items]          
Property, Plant, and Equipment Useful Life 5 years        
Property, Plant and Equipment [Member] | Maximum          
Property, Plant and Equipment [Line Items]          
Property, Plant, and Equipment Useful Life 30 years        
Ground property and equipment          
Property, Plant and Equipment [Line Items]          
Minimum percentage of cost estimated residual value (in hundredths) 0.00%luv_PropertyPlantAndEquipmentPercentageCostToResidualValueMinimum
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_OtherCapitalizedPropertyPlantAndEquipmentMember		        
Maximum percentage of cost estimated as residual value (in hundredths) 10.00%luv_PropertyPlantAndEquipmentPercentageCostToResidualValueMaximum
/ us-gaap_PropertyPlantAndEquipmentByTypeAxis
= us-gaap_OtherCapitalizedPropertyPlantAndEquipmentMember		        
Software | Minimum          
Property, Plant and Equipment [Line Items]          
Property, Plant, and Equipment Useful Life 5 years 0 months 0 days        
Software | Maximum          
Property, Plant and Equipment [Line Items]          
Property, Plant, and Equipment Useful Life 15 years 0 months 0 days        
Change In Estimated Useful Life          
Change in Accounting Estimate [Line Items]          
Change In Accounting Estimate Financial Effect On Depreciation Expense     12,000,000luv_ChangeInAccountingEstimateFinancialEffectOnDepreciationExpense
/ us-gaap_ChangeInAccountingEstimateByTypeAxis
= luv_ChangeInEstimatedUsefulLifeMember		    
Change in accounting estimate, financial effect on net income     6,000,000luv_ChangeInAccountingEstimateFinancialEffectOnNetIncome
/ us-gaap_ChangeInAccountingEstimateByTypeAxis
= luv_ChangeInEstimatedUsefulLifeMember		    
Change in accounting estimate, financial effect on net income per share (in dollars per share)     $ (0.01)luv_ChangeInAccountingEstimateFinancialEffectOnNetIncomePerShare
/ us-gaap_ChangeInAccountingEstimateByTypeAxis
= luv_ChangeInEstimatedUsefulLifeMember		    
Change In Estimated Residual Values          
Change in Accounting Estimate [Line Items]          
Residual Values Percent Of Original Cost Subsequent To Change       2.00%luv_ResidualValuesPercentOfOriginalCostSubsequentToChange
/ us-gaap_ChangeInAccountingEstimateByTypeAxis
= luv_ChangeInEstimatedResidualValuesMember		  
Change In Accounting Estimate Financial Effect On Depreciation Expense     34,000,000luv_ChangeInAccountingEstimateFinancialEffectOnDepreciationExpense
/ us-gaap_ChangeInAccountingEstimateByTypeAxis
= luv_ChangeInEstimatedResidualValuesMember		    
Change in accounting estimate, financial effect on net income     18,000,000luv_ChangeInAccountingEstimateFinancialEffectOnNetIncome
/ us-gaap_ChangeInAccountingEstimateByTypeAxis
= luv_ChangeInEstimatedResidualValuesMember		    
Change in accounting estimate, financial effect on net income per share (in dollars per share)     $ 0.02luv_ChangeInAccountingEstimateFinancialEffectOnNetIncomePerShare
/ us-gaap_ChangeInAccountingEstimateByTypeAxis
= luv_ChangeInEstimatedResidualValuesMember		    
Residual Values Percent Of Original Cost Prior To Change       10.00%luv_ResidualValuesPercentOfOriginalCostPriorToChange
/ us-gaap_ChangeInAccountingEstimateByTypeAxis
= luv_ChangeInEstimatedResidualValuesMember		  
Change in Spoilage Estimate [Domain]          
Change in Accounting Estimate [Line Items]          
Change in Accounting Estimate Financial Effect on Passenger Revenue         55,000,000luv_ChangeinAccountingEstimateFinancialEffectonPassengerRevenueSpoilageEstimate
/ us-gaap_ChangeInAccountingEstimateByTypeAxis
= luv_ChangeinSpoilageEstimateDomain
Change in accounting estimate, financial effect on net income, spoilage adjustment 29,000,000luv_Changeinaccountingestimatefinancialeffectonnetincomespoilageadjustment
/ us-gaap_ChangeInAccountingEstimateByTypeAxis
= luv_ChangeinSpoilageEstimateDomain		        
Change in accounting estimate,financial effect on earnings per share $ 0.04luv_Changeinaccountingestimatefinancialeffectonearningspershare
/ us-gaap_ChangeInAccountingEstimateByTypeAxis
= luv_ChangeinSpoilageEstimateDomain		        
Fuel derivatives          
Accounting Policies [Abstract]          
Total collateral already posted aggregate fair value 266,000,000luv_TotalCollateralAlreadyPostedAggregateFairValue
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_CommodityContractMember		 0luv_TotalCollateralAlreadyPostedAggregateFairValue
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_CommodityContractMember		     266,000,000luv_TotalCollateralAlreadyPostedAggregateFairValue
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_CommodityContractMember
Other Noncurrent Liabilities | Fuel derivatives          
Property, Plant and Equipment [Line Items]          
Collateral Already Posted, Aggregate Fair Value 198,000,000us-gaap_CollateralAlreadyPostedAggregateFairValue
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_OtherNoncurrentLiabilitiesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_CommodityContractMember		 0us-gaap_CollateralAlreadyPostedAggregateFairValue
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_OtherNoncurrentLiabilitiesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_CommodityContractMember		     198,000,000us-gaap_CollateralAlreadyPostedAggregateFairValue
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_OtherNoncurrentLiabilitiesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_CommodityContractMember
Other Noncurrent Liabilities | Interest rate derivatives          
Property, Plant and Equipment [Line Items]          
Collateral Already Posted, Aggregate Fair Value $ 0us-gaap_CollateralAlreadyPostedAggregateFairValue
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_OtherNoncurrentLiabilitiesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember		 $ 32,000,000us-gaap_CollateralAlreadyPostedAggregateFairValue
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_OtherNoncurrentLiabilitiesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember		     $ 0us-gaap_CollateralAlreadyPostedAggregateFairValue
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_OtherNoncurrentLiabilitiesMember
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_InterestRateSwapMember
Unionized Employees concentration risk          
Concentration Risk [Line Items]          
The percentage of Company's employees that are unionized and covered by collective bargaining agreements (in hundredths) 83.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_UnionizedEmployeesConcentrationRiskMember		        
[1] Useful life of leased slots is based on the stated lease term.