Accordian Feature on Short-term Debt

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- Definition

Aircraft Subject to Secure Debt Transactions

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Convertible Debt Conversion Terms Measurement Period Trading Price Threshold Percentage

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Convertible Debt Conversion Terms Percentage of Sales Price Exceeding Conversion Price

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- Definition

Debt Instrument Net of fees

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- Definition

Debt Instrument Underwriters Option to Purchase

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- Definition

Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal Thereafter

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Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Six

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Operating Leases, Future Minimum Payments, Due Thereafter Year 6

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Operating Leases Future Minimum Payments Due in Six Years

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Required Minimum Liquidity Level at All Times After March 31, 2021

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Sale Leaseback Cash Proceeds Investing

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Adjustment to additional paid in capital resulting from the recognition of convertible debt instruments as two separate components - a debt component and an equity component. This bifurcation may result in a basis difference associated with the liability component that represents a temporary difference for purposes of applying accounting for income taxes. The initial recognition of deferred taxes for the tax effect of that temporary difference is as an adjustment to additional paid in capital.

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Exercise price per share or per unit of warrants or rights outstanding.

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Face amount or stated value per share of common stock.

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Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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The carrying amount of the equity component of convertible debt which may be settled in cash upon conversion.

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The price per share of the conversion feature embedded in the debt instrument.

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Ratio applied to the conversion of debt instrument into equity with equity shares divided by debt principal amount.

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Face (par) amount of debt instrument at time of issuance.

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Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

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Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

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Fair value of the amount outstanding under the credit facility.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Principal amount of long-term debt and capital lease obligation maturing in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Principal amount of long-term debt and capital lease obligation maturing in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Principal amount of long-term debt and capital lease obligation maturing in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Principal amount of long-term debt and capital lease obligation maturing in the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of long-term debt and capital lease obligation maturing in the remainder of the fiscal year following the latest fiscal year ended.

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Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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The cash inflow from the additional capital contribution to the entity.

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The cash inflow during the period from additional borrowings in aggregate debt. Includes proceeds from short-term and long-term debt.

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The cash outflow for a long-term debt where the holder has highest claim on the entity's asset in case of bankruptcy or liquidation during the period.

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Amount of gain (loss) on sale and leaseback transaction from transfer of asset accounted for as sale.

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A description of the transaction and the assets involved in the sale of property to another party and the lease of the property back to the seller.

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A description of the terms of the lease(s) related to the assets being leased-back in connection with the transaction involving the sale of property to another party and the lease of the property back to the seller.

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Per share or per unit amount of equity securities issued.

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FINANCING ACTIVITIES (Details) $ / shares in Units, shares in Millions			3 Months Ended			9 Months Ended
	Oct. 05, 2020 USD ($)	May 01, 2020 USD ($) $ / shares shares	Sep. 30, 2020 USD ($) aircraft $ / shares	Jun. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) aircraft $ / shares	Sep. 30, 2019 USD ($)	Jul. 31, 2020 USD ($)	Jun. 08, 2020 USD ($)	May 04, 2020 USD ($)	Apr. 24, 2020 USD ($)	Apr. 09, 2020 $ / shares	Apr. 01, 2020 USD ($)	Mar. 30, 2020 USD ($)
Debt Instrument [Line Items]
Required Minimum Liquidity Level at All Times After March 31, 2021			$ 2,500,000,000			$ 2,500,000,000
Remainder of 2020			543,000,000			543,000,000
2021			220,000,000			220,000,000
2022			524,000,000			524,000,000
2023			1,400,000,000			1,400,000,000
2024			152,000,000			152,000,000
2025			4,000,000,000.0			4,000,000,000.0
Beyond 2025			4,500,000,000			4,500,000,000
Shares Issued, Price Per Share \| $ / shares		$ 28.50
Stock Issued During Period, Shares, New Issues \| shares		80.5
Common Stock, Par or Stated Value Per Share \| $ / shares		$ 1.00
Gain on sale-leaseback transactions			0		$ 0	(222,000,000)	$ 0
Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt				$ (392,000,000)
Proceeds from issuance of long-term debt			1,125,000,000		0	5,622,000,000	0
Debt Instrument, Face Amount									$ 1,800,000,000	$ 2,000,000,000.0
Issuance of common stock			0		0	2,294,000,000	0
Proceeds from sale-leaseback transactions			0		$ 0	815,000,000	$ 0
LUV Common Stock Warrants
Debt Instrument [Line Items]
Class of Warrant or Right, Exercise Price of Warrants or Rights \| $ / shares												$ 36.47
Underwriters' Option [Member]
Debt Instrument [Line Items]
Stock Issued During Period, Shares, New Issues \| shares		10.5
2Q20 Saleleaseback of 10 737-800 and 10 737 MAX 8 aircraft [Member]
Debt Instrument [Line Items]
Sale Leaseback Operating Lease Obligations - 2021			71,000,000			71,000,000
Sale Leaseback Operating Lease Obligations - 2022			71,000,000			71,000,000
Sale Leaseback Operating Lease Obligations - 2023			71,000,000			71,000,000
Sale Leaseback Operating Lease Obligations - 2024			71,000,000			71,000,000
Sale Leaseback Operating Lease Obligations - 2025			71,000,000			71,000,000
Operating Leases, Future Minimum Payments, Remainder of Fiscal Year			18,000,000			18,000,000
Operating Leases, Future Minimum Payments, Due Thereafter			$ 440,000,000			$ 440,000,000
B-737-800
Debt Instrument [Line Items]
Sale Leaseback Transaction, Description of Asset(s)			ten
Gain on sale-leaseback transactions			$ 153,000,000
Sale Leaseback Transaction, Lease Terms			ten years
Proceeds from sale-leaseback transactions			$ 405,000,000
B-737-7 MAX
Debt Instrument [Line Items]
Sale Leaseback Transaction, Description of Asset(s)			ten
Gain on sale-leaseback transactions			$ 69,000,000
Sale Leaseback Transaction, Lease Terms			13 years
Proceeds from sale-leaseback transactions			$ 410,000,000
2.625% Notes due 2030
Debt Instrument [Line Items]
Stated interest rate			2.625%			2.625%
Unsecured Debt			$ 500,000,000			$ 500,000,000
Amended 364-Day Term Loan Credit Facility
Debt Instrument [Line Items]
Debt Instrument, Face Amount													$ 2,300,000,000
1.250 Convertible Senior Notes due 2025
Debt Instrument [Line Items]
Stated interest rate		1.25%
Debt Instrument, Convertible, Conversion Price \| $ / shares			$ 38.48			$ 38.48
Debt Instrument, Convertible, Conversion Ratio			25.9909
Debt Instrument, Redemption Price, Percentage			100.00%
Convertible Debt Conversion Terms Percentage of Sales Price Exceeding Conversion Price			130.00%
Convertible Debt Conversion Terms Measurement Period Trading Price Threshold Percentage			98.00%
4.750 Unsecured Notes due 2023
Debt Instrument [Line Items]
Stated interest rate									4.75%	4.75%
Debt Instrument, Face Amount									$ 500,000,000	$ 750,000,000
5.250 Unsecured Notes due 2025
Debt Instrument [Line Items]
Stated interest rate										5.25%
Debt Instrument, Face Amount										$ 1,250,000,000
5.125 Unsecured Notes due 2027 [Member]
Debt Instrument [Line Items]
Stated interest rate									5.125%
Debt Instrument, Face Amount									$ 1,300,000,000
4.750 Unsecured Notes due 2023 and 5.125 Unsecured Notes due 2027 [Member]
Debt Instrument [Line Items]
Proceeds from issuance of long-term debt			$ 1,700,000,000
Secured Debt by Six Aircraft [Member]
Debt Instrument [Line Items]
Aircraft Subject to Secure Debt Transactions \| aircraft			6			6
Debt Instrument, Face Amount			$ 192,000,000			$ 192,000,000
364-Day Term Loan Credit Facility
Debt Instrument [Line Items]
Debt Instrument, Face Amount			$ 1,000,000,000.0			$ 1,000,000,000.0
Secured Debt by Four Aircraft [Member]
Debt Instrument [Line Items]
Aircraft Subject to Secure Debt Transactions \| aircraft			4			4
Debt Instrument, Face Amount			$ 125,000,000			$ 125,000,000
Debt Instrument Net of fees			$ 121,000,000			$ 121,000,000
Secured Debt by Four Aircraft [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Stated interest rate			1.40%			1.40%
Convertible Debt [Member] \| 1.250 Convertible Senior Notes due 2025
Debt Instrument [Line Items]
Stated interest rate		1.25%
Debt Instrument Underwriters Option to Purchase		$ 300,000,000
Adjustments to Additional Paid in Capital, Equity Component of Convertible Debt			$ (11,000,000)
Debt Instrument, Interest Rate, Effective Percentage			5.20%			5.20%
Debt Instrument, Face Amount		$ 2,300,000,000	$ 1,900,000,000			$ 1,900,000,000
Debt Instrument, Convertible, Carrying Amount of Equity Component			(403,000,000)			(403,000,000)
Unamortized Debt Issuance Expense			62,000,000			62,000,000
Carrying amount of debt			$ 1,927,000,000			$ 1,927,000,000
Unsecured Debt \| 2.625% Notes due 2030
Debt Instrument [Line Items]
Stated interest rate			2.625%			2.625%
Carrying amount of debt			$ 500,000,000			$ 500,000,000
Unsecured Debt \| 1.250 Convertible Senior Notes due 2025
Debt Instrument [Line Items]
Stated interest rate			1.25%			1.25%
Unsecured Debt \| 4.750 Unsecured Notes due 2023
Debt Instrument [Line Items]
Stated interest rate			4.75%			4.75%
Carrying amount of debt			$ 1,250,000,000			$ 1,250,000,000
Unsecured Debt \| 5.250 Unsecured Notes due 2025
Debt Instrument [Line Items]
Stated interest rate			5.25%			5.25%
Carrying amount of debt			$ 1,550,000,000			$ 1,550,000,000		$ 300,000,000
Unsecured Debt \| 5.125 Notes due 2027
Debt Instrument [Line Items]
Stated interest rate			5.125%			5.125%
Carrying amount of debt			$ 2,000,000,000			$ 2,000,000,000		700,000,000
Unsecured Debt \| 5.250 Unsecured Notes due 2025 and 5.125 Notes due 2027 [Member]
Debt Instrument [Line Items]
Carrying amount of debt								$ 1,000,000,000.0
Unsecured Debt \| 2.65% Notes due 2020
Debt Instrument [Line Items]
Stated interest rate			2.65%			2.65%
Carrying amount of debt			$ 500,000,000			$ 500,000,000
Unsecured Debt \| 2.65% Notes due 2020 \| Subsequent Event
Debt Instrument [Line Items]
Stated interest rate	2.65%
Repayments of Senior Debt	$ 500,000,000
Revolving Credit Facility
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity			$ 1,500,000,000			$ 1,500,000,000
Amended 364-Day Term Loan Credit Facility \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Stated interest rate			1.00%			1.00%
Amended 364-Day Term Loan Credit Facility \| London Interbank Offered Rate (LIBOR) [Member] \| Minimum
Debt Instrument [Line Items]
Stated interest rate			1.00%			1.00%
Amended 364-Day Term Loan Credit Facility \| New York Fed Bank Rate [Member]
Debt Instrument [Line Items]
Stated interest rate			0.50%			0.50%
Amended 364-Day Term Loan Credit Facility \| Base Rate [Member] \| Minimum
Debt Instrument [Line Items]
Stated interest rate			1.00%			1.00%
Accordian Feature to Amended 364-Day Term Loan Credit Facility [Member] \| Amended 364-Day Term Loan Credit Facility
Debt Instrument [Line Items]
Accordian Feature on Short-term Debt														$ 417,000,000
Debt Instrument, Face Amount											$ 350,000,000
Secured Debt by Six Aircraft [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Stated interest rate			1.40%			1.40%
Existing Revolving Credit Facility [Member] \| Revolving Credit Facility
Debt Instrument [Line Items]
Line of Credit Facility, Current Borrowing Capacity			$ 1,000,000,000.0			$ 1,000,000,000.0
Revolving Credit Facility, Fair Value Amount Outstanding			0			0
Existing Revolving Credit Facility [Member] \| 364-Day Term Loan Credit Facility
Debt Instrument [Line Items]
Debt Instrument, Face Amount			$ 1,000,000,000.0			$ 1,000,000,000.0