Document And Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2020	Feb. 04, 2021	Jun. 30, 2020
Entity Incorporation, State or Country Code	TX
Entity Tax Identification Number	74-1563240
Document Transition Report	false
Document Annual Report	true
Entity Address, Address Line One	P.O. Box 36611
Entity Address, City or Town	Dallas,
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	75235-1611
City Area Code	214
ICFR Auditor Attestation Flag	true
Local Phone Number	792-4000
Title of 12(g) Security	None
Entity Registrant Name	SOUTHWEST AIRLINES CO.
Entity Central Index Key	0000092380
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2020
Entity File Number	1-7259
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding		590,677,474
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Public Float			$ 20,094,518,012
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
NEW YORK STOCK EXCHANGE, INC. [Member]
Title of 12(b) Security	Common Stock ($1.00 par value)
Trading Symbol	LUV
Security Exchange Name	NYSE