Supplemental Financial Information - Accounts and Other Receivables (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Accounts and Other Receivables [Abstract]
Trade receivables	$ 53	$ 57
Credit card receivables	112	107
Business partners and other suppliers	779	319
Income tax receivable	87	22
Other	55	63
Accounts and other receivables	$ 1,086	$ 568

Accounts and Other Receivables [Abstract]

No definition available.

Name:	luv_AccountsandOtherReceivablesAbstract
Namespace Prefix:	luv_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

BusinessPartnersAndOtherSuppliers

+ References

No definition available.

+ Details

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

- Definition

Trade Receivables

+ References

No definition available.

+ Details

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

- Definition

Amount, after allowance, receivable from customers, clients, or other third-parties, and receivables classified as other due within one year or the normal operating cycle, if longer.

+ References

No definition available.

+ Details

Name:	us-gaap_AccountsAndOtherReceivablesNetCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amounts receivable from issuing a card to individuals or businesses that allows someone to make a purchase on borrowed money.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.8)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_CreditCardReceivables
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Carrying amount due within one year of the balance sheet date (or one operating cycle, if longer) from tax authorities as of the balance sheet date representing refunds of overpayments or recoveries based on agreed-upon resolutions of disputes.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.5(c))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.10)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.3(a)(4))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_IncomeTaxesReceivable
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, after allowance, of receivables classified as other, due within one year or the operating cycle, if longer.

+ References

No definition available.

+ Details

Name:	us-gaap_OtherReceivablesNetCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant