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Long-term Debt (Details) | 12 Months Ended
--- | ---
Dec. 31, 2018 USD ($) aircraft Mortgages Agreements | Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($)
Debt Instrument [Line Items] |  |  |
Encumbered Aircraft Released | aircraft | 1 |  |
Encumbered Aircraft Remaining | aircraft | 4 |  |
Repayments of Convertible Debt | $ 0 | $ 0 | $ 68,000,000
Letters of Credit Outstanding Amount | 170,000,000 |  |
Net book value of assets pledged as collateral for the Company's secured borrowings, primarily aircraft and engines | 1,500,000,000 |  |
Net book value of additional assets pledged as collateral in case obligations related to fuel derivatives exceed certain thresholds | 2,100,000,000 |  |
Long-term Debt, by Maturity [Abstract] |  |  |
2019 | 590,000,000 |  |
2020 | 821,000,000 |  |
2021 | 172,000,000 |  |
2022 | 477,000,000 |  |
2023 | 105,000,000 |  |
Thereafter | 1,100,000,000 |  |
AirTran Airways | Interest rate derivatives |  |  |
Debt Instrument [Line Items] |  |  |
Notional amount | $ 57,000,000 |  |
AirTran Airways | Maximum | Interest rate derivatives |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate stated in the debt agreement (in hundredths) | 5.91% |  |
French Credit Agreements due June 2018 - 2.54% |  |  |
Debt Instrument [Line Items] |  |  |
Face amount of debt | $ 112,000,000 |  |
Interest rate stated in the debt agreement (in hundredths) |  | 2.54% |
Number of identical floating rate financing agreements entered into concurrently with French banking partnerships | Agreements | 4 |  |
Term | 13 years |  |
Fixed-rate 737 Aircraft Notes payable through January 2018 - 7.03% |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate stated in the debt agreement (in hundredths) |  | 7.03% |
2.75% Unsecured Senior Notes Due November 2019 |  |  |
Debt Instrument [Line Items] |  |  |
Face amount of debt | $ 300,000,000 |  |
Interest rate stated in the debt agreement (in hundredths) | 2.75% |  |
Term Loan Agreement payable through May 2019 - 6.315% |  |  |
Debt Instrument [Line Items] |  |  |
Number of mortgages on secured aircraft | Mortgages | 14 |  |
Interest rate stated in the debt agreement (in hundredths) | 6.315% |  |
Term Loan Agreement payable through May 2019 - 6.315% | LIBOR |  |  |
Debt Instrument [Line Items] |  |  |
Spread on variable rate | 3.30% |  |
Term Loan Agreement payable through May 2019 - 6.315% | Maximum |  |  |
Debt Instrument [Line Items] |  |  |
Face amount of debt | $ 332,000,000 |  |
Term Loan Agreement payable through July 2019 - 4.84% |  |  |
Debt Instrument [Line Items] |  |  |
Number of mortgages on secured aircraft | Mortgages | 5 |  |
Interest rate stated in the debt agreement (in hundredths) | 4.84% |  |
Debt Instrument, Prepayment Amount | $ 24,000,000 |  |
Term Loan Agreement payable through July 2019 - 4.84% | Maximum |  |  |
Debt Instrument [Line Items] |  |  |
Face amount of debt | 124,000,000 |  |
2.65% Notes due 2020 |  |  |
Debt Instrument [Line Items] |  |  |
Face amount of debt | $ 500,000,000 |  |
Interest rate stated in the debt agreement (in hundredths) | 2.65% |  |
Term Loan Agreement payable through 2020 - 5.223% |  |  |
Debt Instrument [Line Items] |  |  |
Number of mortgages on secured aircraft | Mortgages | 21 |  |
Face amount of debt | $ 600,000,000 |  |
Interest rate stated in the debt agreement (in hundredths) | 5.223% |  |
Term Loan Agreement payable through 2020 - 5.223% | LIBOR |  |  |
Debt Instrument [Line Items] |  |  |
Spread on variable rate | 0.95% |  |
737 Aircraft Notes payable through 2020 | AirTran Airways |  |  |
Debt Instrument [Line Items] |  |  |
Number of mortgages on secured aircraft | Mortgages | 9 |  |
Weighted average interest rate | 4.06% |  |
Notes Payable Aircraft Fixed Rate Through 2019 [Member] | AirTran Airways |  |  |
Debt Instrument [Line Items] |  |  |
Number of mortgages on secured aircraft | Mortgages | 1 |  |
Unsecured Senior Notes Due 2022 - 2.75% |  |  |
Debt Instrument [Line Items] |  |  |
Face amount of debt | $ 300,000,000 |  |
Interest rate stated in the debt agreement (in hundredths) | 2.75% |  |
Pass Through Certificates due 2022 - 6.24% |  |  |
Debt Instrument [Line Items] |  |  |
Number of mortgages on secured aircraft | Mortgages | 16 |  |
Face amount of debt | $ 500,000,000 |  |
Pass Through Certificates due 2022 - 6.24% | Interest rate derivatives | Cash Flow Hedging |  |  |
Debt Instrument [Line Items] |  |  |
Notional amount | 20,000,000 |  |
Pass Through Certificates Series A |  |  |
Debt Instrument [Line Items] |  |  |
Face amount of debt | $ 412,000,000 |  |
Interest rate stated in the debt agreement (in hundredths) | 6.15% |  |
Pass Through Certificates Series B |  |  |
Debt Instrument [Line Items] |  |  |
Face amount of debt | $ 88,000,000 |  |
Interest rate stated in the debt agreement (in hundredths) | 6.65% |  |
Term Loan Agreement Due 2026 - 3.88% |  |  |
Debt Instrument [Line Items] |  |  |
Number of mortgages on secured aircraft | Mortgages | 7 |  |
Interest rate stated in the debt agreement (in hundredths) | 3.88% |  |
Term Loan Agreement Due 2026 - 3.88% | LIBOR |  |  |
Debt Instrument [Line Items] |  |  |
Spread on variable rate | 1.10% |  |
Term Loan Agreement Due 2026 - 3.88% | Maximum |  |  |
Debt Instrument [Line Items] |  |  |
Face amount of debt | $ 215,000,000 |  |
Unsecured Senior Notes Due 2026 - 3.00% |  |  |
Debt Instrument [Line Items] |  |  |
Face amount of debt | $ 300,000,000 |  |
Interest rate stated in the debt agreement (in hundredths) | 3.00% |  |
Unsecured Senior Notes Due 2027 - 3.45% |  |  |
Debt Instrument [Line Items] |  |  |
Face amount of debt | $ 300,000,000 |  |
Interest rate stated in the debt agreement (in hundredths) | 3.45% |  |
Unsecured Senior Notes Due 2027 - 3.45% | Treasury Rate |  |  |
Debt Instrument [Line Items] |  |  |
Spread on variable rate | 20.00% |  |
7.375% Debentures due 2027 |  |  |
Debt Instrument [Line Items] |  |  |
Face amount of debt | $ 100,000,000 |  |
Interest rate stated in the debt agreement (in hundredths) | 7.375% |  |
Enhanced Equipment Trust Certificate | Pass Through Certificates due 2022 - 6.24% |  |  |
Debt Instrument [Line Items] |  |  |
Interest rate stated in the debt agreement (in hundredths) | 6.24% |  |
B-737-700 |  |  |
Debt Instrument [Line Items] |  |  |
Maximum additional number of assets pledged as collateral in case obligations related to fuel derivatives exceed certain thresholds | aircraft | 74 |  |
B-737-800 |  |  |
Debt Instrument [Line Items] |  |  |
Maximum additional number of assets pledged as collateral in case obligations related to fuel derivatives exceed certain thresholds | aircraft | 24 |  |

X
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