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Debt Instrument, Face Amount, Accordion Feature, Incremental Commitments, Amount

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Number Of Payroll Support Programs

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Contractual interest rate for funds borrowed, under the debt agreement.

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- Details

Name:	us-gaap_DebtInstrumentAxis=luv_AmendedCreditAgreementMember
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Data Type:	na
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Period Type:

FINANCING ACTIVITIES (Details) $ in Millions					3 Months Ended			9 Months Ended
FINANCING ACTIVITIES (Details) $ in Millions	Apr. 22, 2026 USD ($)	Dec. 30, 2025 USD ($)	Dec. 29, 2025 USD ($)	Apr. 17, 2025 USD ($)	Sep. 30, 2026 USD ($) program	Sep. 30, 2025 USD ($)	Jun. 30, 2025 USD ($)	Sep. 30, 2026 USD ($) program	Sep. 30, 2025 USD ($)	Aug. 10, 2026 USD ($)	May 19, 2026 USD ($)	Mar. 11, 2026 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	May 01, 2020 USD ($)
Debt Instrument [Line Items]
Number of payroll support programs \| program					3			3
Proceeds from sale and leaseback transactions					$ 212
Gain on sale-leaseback transactions					118	$ 0		$ 118	$ 3
Convertible Debt
Debt Instrument [Line Items]
Face amount of debt															$ 2,300
Principal amount of debt repurchased													$ 689	$ 689
Early repayments of loan							$ 1,600
Convertible Debt \| 1.250 Convertible Senior Notes
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)															1.25%
Unsecured Debt \| 1.000% Payroll Support Program Loan due 2030
Debt Instrument [Line Items]
Early repayments of loan				$ 976
Unsecured Debt \| 2.0 Payroll Support Program Loan due 2031
Debt Instrument [Line Items]
Early repayments of loan			$ 566
Unsecured Debt \| 3.0 Payroll Support Program Loan due 2031
Debt Instrument [Line Items]
Early repayments of loan		$ 100
Unsecured Debt \| 1.0 Payroll Support Program Loan due 2031
Debt Instrument [Line Items]
Early repayments of loan	$ 426
Secured Debt \| Term Loan Credit Agreement
Debt Instrument [Line Items]
Face amount of debt					1,500			1,500				$ 500
Accordion feature incremental commitments											$ 1,000	$ 1,000
Accordion feature incremental commitments											$ 1,000
Secured Debt \| Term Loan Credit Agreement \| Secured Overnight Financing Rate (SOFR)
Debt Instrument [Line Items]
Floor percentage												0.00%
Secured Debt \| Term Loan Credit Agreement \| Base Rate
Debt Instrument [Line Items]
Floor percentage												1.00%
Line of Credit \| Credit Agreement \| Revolving Credit Facility
Debt Instrument [Line Items]
Borrowing capacity										$ 2,000
Line of Credit \| Amended Credit Agreement \| Revolving Credit Facility
Debt Instrument [Line Items]
Accordion feature incremental commitments										$ 3,000
Credit outstanding					$ 0	$ 0		$ 0	$ 0