Basis of Presentation (Policies)	6 Months Ended
Basis of Presentation (Policies)	Jun. 30, 2016
Accounting Policies [Abstract]
Basis of Presentation	The unaudited Condensed Consolidated Financial Statements for the interim periods ended June 30, 2016 and 2015 include all adjustments which are, in the opinion of management, necessary for a fair presentation of the results for the interim periods. This includes all normal and recurring adjustments and elimination of significant intercompany transactions. Financial results for the Company and airlines in general can be seasonal in nature. In many years, the Company's revenues, as well as its operating income and net income, have been better in its second and third fiscal quarters than in its first and fourth fiscal quarters. Air travel is also significantly impacted by general economic conditions, the amount of disposable income available to consumers, unemployment levels, corporate travel budgets, and other factors beyond the Company's control. These and other factors, such as the price of jet fuel in some periods, the nature of the Company's fuel hedging program, the periodic volatility of commodities used by the Company for hedging jet fuel, and the requirements related to hedge accounting, have created, and may continue to create, significant volatility in the Company's financial results. See Note 3 for further information on fuel and the Company's hedging program. Operating results for the three and six months ended June 30, 2016, are not necessarily indicative of the results that may be expected for future quarters or for the year ended December 31, 2016. For further information, refer to the Consolidated Financial Statements and footnotes thereto included in the Southwest Airlines Co. Annual Report on Form 10-K for the year ended December 31, 2015.
Derivatives	The Company is party to certain interest rate swap agreements that are accounted for as either fair value hedges or cash flow hedges, as defined in the applicable accounting guidance for derivative instruments and hedging. Several of the Company's interest rate swap agreements qualify for the “shortcut” method of accounting for hedges, which dictates that the hedges are assumed to be perfectly effective, and, thus, there is no ineffectiveness to be recorded in earnings. For the Company’s interest rate swap agreements that do not qualify for the "shortcut" method of accounting, ineffectiveness is required to be measured at each reporting period. The ineffectiveness associated with all of the Company’s interest rate hedges for all periods presented was not material. Upon proper qualification, the Company accounts for its fuel derivative instruments as cash flow hedges. Generally, utilizing hedge accounting, all periodic changes in fair value of the derivatives designated as hedges that are considered to be effective are recorded in Accumulated other comprehensive income (loss) ("AOCI") until the underlying jet fuel is consumed. See Note 4. The Company’s results are subject to the possibility that periodic changes will not be effective, as defined, or that the derivatives will no longer qualify for hedge accounting. Ineffectiveness results when the change in the fair value of the derivative instrument exceeds the change in the value of the Company’s expected future cash outlay to purchase and consume jet fuel. To the extent that the periodic changes in the fair value of the derivatives are ineffective, the ineffective portion is recorded to Other (gains) losses, net, in the unaudited Condensed Consolidated Statement of Comprehensive Income. Likewise, if a hedge ceases to qualify for hedge accounting, any change in the fair value of derivative instruments since the last reporting period is recorded to Other (gains) losses, net, in the unaudited Condensed Consolidated Statement of Comprehensive Income in the period of the change; however, any amounts previously recorded to AOCI would remain there until such time as the original forecasted transaction occurs, at which time these amounts would be reclassified to Fuel and oil expense. When the Company has sold derivative positions in order to effectively “close” or offset a derivative already held as part of its fuel derivative instrument portfolio, any subsequent changes in fair value of those positions are marked to market through earnings. Likewise, any changes in fair value of those positions that were offset by entering into the sold positions and were de-designated as hedges are concurrently marked to market through earnings. However, any changes in value related to hedges that were deferred as part of AOCI while designated as a hedge would remain until the originally forecasted transaction occurs. In a situation where it becomes probable that a fuel hedged forecasted transaction will not occur, any gains and/or losses that have been recorded to AOCI would be required to be immediately reclassified into earnings. The Company did not have any such situations occur during 2015, or during the six months ended June 30, 2016.
Fair Value of Financial Instruments	Accounting standards pertaining to fair value measurements establish a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value. These tiers include: Level 1, defined as observable inputs such as quoted prices in active markets; Level 2, defined as inputs other than quoted prices in active markets that are either directly or indirectly observable; and Level 3, defined as unobservable inputs in which little or no market data exists, therefore requiring an entity to develop its own assumptions. As of June 30, 2016, the Company held certain items that are required to be measured at fair value on a recurring basis. These included cash equivalents, short-term investments (primarily treasury bills and certificates of deposit), interest rate derivative contracts, fuel derivative contracts, and available-for-sale securities. The majority of the Company’s short-term investments consist of instruments classified as Level 1. However, the Company has certificates of deposit, commercial paper, and Eurodollar time deposits that are classified as Level 2, due to the fact that the fair value for these instruments is determined utilizing observable inputs in non-active markets. Other available-for-sale securities primarily consist of investments associated with the Company’s excess benefit plan. The Company’s fuel and interest rate derivative instruments consist of over-the-counter contracts, which are not traded on a public exchange. Fuel derivative instruments include swaps, as well as different types of option contracts, whereas interest rate derivatives consist solely of swap agreements. See Note 3 for further information on the Company’s derivative instruments and hedging activities. The fair values of swap contracts are determined based on inputs that are readily available in public markets or can be derived from information available in publicly quoted markets. Therefore, the Company has categorized these swap contracts as Level 2. The Company’s Treasury Department, which reports to the Chief Financial Officer, determines the value of option contracts utilizing an option pricing model based on inputs that are either readily available in public markets, can be derived from information available in publicly quoted markets, or are provided by financial institutions that trade these contracts. The option pricing model used by the Company is an industry standard model for valuing options and is the same model used by the broker/dealer community (i.e., the Company’s counterparties). The inputs to this option pricing model are the option strike price, underlying price, risk free rate of interest, time to expiration, and volatility. Because certain inputs used to determine the fair value of option contracts are unobservable (principally implied volatility), the Company has categorized these option contracts as Level 3. Volatility information is obtained from external sources, but is analyzed by the Company for reasonableness and compared to similar information received from other external sources. The fair value of option contracts considers both the intrinsic value and any remaining time value associated with those derivatives that have not yet settled. The Company also considers counterparty credit risk and its own credit risk in its determination of all estimated fair values. To validate the reasonableness of the Company’s option pricing model, on a monthly basis, the Company compares its option valuations to third party valuations. If any significant differences were to be noted, they would be researched in order to determine the reason. However, historically, no significant differences have been noted. The Company has consistently applied these valuation techniques in all periods presented and believes it has obtained the most accurate information available for the types of derivative contracts it holds.
Revenue Recognition, Multiple-deliverable Arrangements, Description	The Company sells frequent flyer points and related services to companies participating in its frequent flyer program. Historically, funds received from the sale of points associated with these agreements were accounted for under the residual method. Under this method, the Company estimated the portion of the amounts received from the sale of frequent flyer points that related to free travel and these amounts were deferred and recognized as Passenger revenue when the ultimate free travel awards were flown. On July 1, 2015, the Company executed an amended co-branded credit card agreement ("Agreement") with Chase Bank USA, N.A. (“Chase”), through which the Company sells loyalty points and other items to Chase. This material modification triggered an accounting change under ASU No. 2009-13, which has been recorded on a prospective basis. The impact of the accounting change is that the Company estimated the selling prices and volumes over the term of the Agreement in order to determine the allocation of proceeds to each of the deliverables (travel points to be awarded; use of the Southwest Airlines’ brand and access to Rapid Reward Member lists; advertising elements; and the Company’s resource team). The Company records passenger revenue related to air transportation and certificates for discounted companion travel when the transportation is delivered. The other elements are recognized as Other revenue when earned. The Company followed the transition approach of ASU No. 2009-13, which required that the Company adjust the existing deferred revenue balance to reflect the value, on a relative selling price basis, of any undelivered element remaining at the date of contract modification. The relative selling price of the undelivered element (air transportation) was lower than the rate at which it had been deferred under the residual method.
New Accounting Pronouncements	On June 16, 2016, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2016-13, Accounting for Credit Losses. The new standard requires the use of an “expected loss” model on certain types of financial instruments. The standard also amends the impairment model for available-for-sale debt securities and requires estimated credit losses to be recorded as allowances instead of reductions to amortized cost of the securities. This ASU is effective for fiscal years, and interim periods within those years, beginning after December 15, 2019, with early adoption permitted. The Company is evaluating the new guidance and plans to provide additional information at a future date. On March 30, 2016, the FASB issued ASU No. 2016-09, Improvements to Employee Share-Based Payment Accounting. The standard is part of the FASB effort to simplify various aspects related to how share-based payments are accounted for and presented in the financial statements. This ASU is effective for fiscal years, and interim periods within those years, beginning after December 15, 2016. Early adoption is permitted in any interim or annual period, with any adjustments reflected as of the beginning of the fiscal year of adoption. The Company early adopted this standard during the three months ended June 30, 2016, with an effective date as of January 1, 2016. The prospective method of adoption of this standard resulted in the recognition of $5 million and $7 million of excess tax benefits to the Company's income tax provision for the three and six months ended June 30, 2016, respectively. On February 25, 2016, the FASB issued ASU No. 2016-02, Leases. The standard is effective for fiscal years, and interim periods within those years, beginning after December 15, 2018, with early adoption permitted. The Company believes the most significant impact of this ASU will be the presentation of operating leases with durations greater than twelve months, with certain exceptions, on the balance sheet. The Company is evaluating the new guidance and plans to provide additional information about its expected financial impact at a future date. On May 28, 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers. Following the FASB's finalization of a one year deferral of this standard, the ASU is now effective for fiscal years, and interim periods within those years, beginning on or after December 15, 2017, with early adoption permitted for fiscal years, and interim periods within those years, beginning on or after December 15, 2016. The Company currently believes the most significant impact of this ASU on its accounting will be the elimination of the incremental cost method for frequent flyer accounting, which will require the Company to re-value its liability associated with flight points earned by Customers with a relative fair value approach, resulting in a significant increase in the liability. The Company is continuing to evaluate the new guidance and plans to provide additional information about its expected financial impact at a future date.

Disclosure of accounting policy for revenue recognition for multiple-deliverable arrangements including, at a minimum (as applicable): (1) the nature of such arrangements, (2) the significant deliverables within the arrangements, (3) the general timing of delivery or performance of service for the deliverables within the arrangements, (4) performance-, cancellation-, termination- or refund-type provisions, (5) a discussion of the significant factors, inputs, assumptions, and methods used to determine selling price (whether vendor-specific objective evidence, third-party evidence, or estimated selling price) for the significant deliverables, (6) whether the significant deliverables in the arrangements qualify as separate units of accounting and the reasons that they do not qualify as separate units of accounting, if applicable, and (7) the general timing of revenue recognition for significant units of accounting. This element is applicable to all multiple-deliverable arrangements, including software arrangements (for example, software products, upgrades or enhancements, postcontract customer support, or services).