Financial Derivative Instruments - Collateral by Balance Sheet Location (Details) - Fuel derivatives - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Accounts Payable
Derivative [Line Items]
Due to third parties for fuel contracts	$ 1	$ 0
Accounts And Other Receivables
Derivative [Line Items]
Receivable from third parties for settled fuel contracts - current	$ 4	$ 2

Amount receivable from third parties for settled fuel contracts as of the end of the period reported, recorded in Accounts and other receivables on the balance sheet.

No definition available.

Name:	luv_ReceivableFromThirdPartiesForSettledFuelContractsCurrent
Namespace Prefix:	luv_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant