Document And Entity Information - shares	9 Months Ended
	Sep. 30, 2020	Oct. 23, 2020
Entity Information [Line Items]
Document Transition Report	false
Entity Incorporation, State or Country Code	TX
Document Quarterly Report	true
Entity Registrant Name	SOUTHWEST AIRLINES CO.
City Area Code	214
Local Phone Number	792-4000
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity Central Index Key	0000092380
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Entity File Number	1-7259
Document Period End Date	Sep. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding		590,273,067
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Tax Identification Number	74-1563240
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
NEW YORK STOCK EXCHANGE, INC. [Member]
Entity Information [Line Items]
Title of 12(b) Security	Common Stock ($1.00 par value)
Trading Symbol	LUV
Security Exchange Name	NYSE