FINANCING ACTIVITIES - Narrative (Details)					12 Months Ended
FINANCING ACTIVITIES - Narrative (Details)	Apr. 20, 2026	Dec. 30, 2025 USD ($)	Dec. 29, 2025 USD ($)	Apr. 17, 2025 USD ($)	Dec. 31, 2025 USD ($) program	Dec. 31, 2022 USD ($)	Nov. 30, 2025 USD ($)	Jun. 30, 2025 USD ($)	Dec. 31, 2024 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Jul. 31, 2020 USD ($)	Jun. 08, 2020 USD ($)	May 01, 2020 USD ($)	Feb. 29, 2020 USD ($)	Nov. 30, 2017 USD ($)	Nov. 30, 2016 USD ($)	Feb. 28, 1997 USD ($)
Debt Instrument [Line Items]
Payroll support programs \| program					3
Outstanding letters of credit					$ 272,000,000
Net book value of assets pledged as collateral for the Company's secured borrowings, primarily aircraft and engines					0
Revolving Credit Facility
Debt Instrument [Line Items]
Credit outstanding					$ 0				$ 0
Convertible Notes
Debt Instrument [Line Items]
Face amount of debt								$ 1,600,000,000						$ 2,300,000,000
Interest rate stated in the debt agreement (as a percent)														1.25%
Principal amount of debt repurchased						$ 689,000,000				$ 689,000,000
Term (in years)					5 years
Line of Credit
Debt Instrument [Line Items]
Maximum borrowing capacity					$ 1,500,000,000
5.250% Notes \| Unsecured Debt
Debt Instrument [Line Items]
Face amount of debt					$ 750,000,000		$ 750,000,000
Interest rate stated in the debt agreement (as a percent)					5.25%		5.25%
4.375% Notes \| Unsecured Debt
Debt Instrument [Line Items]
Face amount of debt							$ 750,000,000
Interest rate stated in the debt agreement (as a percent)					4.375%		4.375%
Total 5.125 Notes due 2027 \| Unsecured Debt
Debt Instrument [Line Items]
Face amount of debt											$ 2,000,000,000
5.125 Unsecured Notes due 2027
Debt Instrument [Line Items]
Face amount of debt													$ 1,300,000,000
5.125% Notes \| Unsecured Debt
Debt Instrument [Line Items]
Face amount of debt												$ 700,000,000
Interest rate stated in the debt agreement (as a percent)					5.125%						5.125%
Early prepayments made on debt						$ 273,000,000
2.625% Notes
Debt Instrument [Line Items]
Face amount of debt															$ 500,000,000
Interest rate stated in the debt agreement (as a percent)															2.625%
2.625% Notes \| Unsecured Debt
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)					2.625%
Unsecured Senior Notes Due 2027 - 3.45%
Debt Instrument [Line Items]
Face amount of debt																$ 300,000,000
Interest rate stated in the debt agreement (as a percent)																3.45%
3.00% Notes
Debt Instrument [Line Items]
Face amount of debt																	$ 300,000,000
Interest rate stated in the debt agreement (as a percent)																	3.00%
3.00% Notes \| Unsecured Debt
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)					3.00%
7.375% Debentures
Debt Instrument [Line Items]
Face amount of debt																		$ 100,000,000
Interest rate stated in the debt agreement (as a percent)																		7.375%
7.375% Debentures \| Unsecured Debt
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)					7.375%
1.000% Payroll Support Program Loan due 2030 \| Unsecured Debt
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)					1.00%
Early repayments of loan				$ 976,000,000
2.0 Payroll Support Program Loan due 2031 \| Unsecured Debt
Debt Instrument [Line Items]
Early repayments of loan			$ 566,000,000
3.0 Payroll Support Program Loan due 2031 \| Unsecured Debt
Debt Instrument [Line Items]
Early repayments of loan		$ 100,000,000
Amended 364-Day Term Loan Credit Facility
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)					1.00%
Amended 364-Day Term Loan Credit Facility \| Minimum
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)					1.00%
Amended 364-Day Term Loan Credit Facility \| Secured Overnight Financing Rate (SOFR)
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)					0.10%
Amended 364-Day Term Loan Credit Facility \| New York Fed Bank Rate
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)					0.50%
Amended 364-Day Term Loan Credit Facility \| Base Rate \| Minimum
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)					1.00%
1.000% Payroll Support Program Loan due 2031 \| Unsecured Debt
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)					1.00%
1.000% Payroll Support Program Loan due 2031 \| Unsecured Debt
Debt Instrument [Line Items]
Interest rate stated in the debt agreement (as a percent)					1.00%
1.000% Payroll Support Program Loan due 2031 \| Unsecured Debt \| Forecast
Debt Instrument [Line Items]
Spread on variable rate (as a percent)	2.00%

SOUTHWEST AIRLINES CO 10-K