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Special Charges and Unrealized (Gains) Losses on Investments - Narrative (Details) | 1 Months Ended | 3 Months Ended | 12 Months Ended
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Jul. 31, 2020 employee | May 31, 2018 USD ($) | Dec. 31, 2020 USD ($) employee plane | Sep. 30, 2020 USD ($) | Jun. 30, 2020 USD ($) | Mar. 31, 2020 USD ($) | Dec. 31, 2019 USD ($) | Sep. 30, 2019 USD ($) | Jun. 30, 2019 USD ($) | Mar. 31, 2019 USD ($) | Mar. 31, 2017 USD ($) employee | Dec. 31, 2020 USD ($) employee plane | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($)
Special Charges [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cash received under the Payroll Support Program |  |  |  |  |  |  |  |  |  |  |  | $ 5,100,000,000 |  |
Cash received from grants |  |  |  |  |  |  |  |  |  |  |  | 3,600,000,000 |  |
Proceeds from the issuance of an unsecured loan |  |  |  |  |  |  |  |  |  |  |  | 1,500,000,000 |  |
Proceeds from issuance of warrants |  |  |  |  |  |  |  |  |  |  |  | 66,000,000 |  |
Portion of grant recognized as a credit to special charges |  |  | $ 453,000,000 | $ 1,494,000,000 | $ 1,589,000,000 | $ 0 |  |  |  |  |  | $ 3,536,000,000 | $ 0 | $ 0
Number of employees notified of plans for workforce reduction | employee | 36,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Number of employee furloughs | employee |  |  | 13,000 |  |  |  |  |  |  |  |  | 13,000 |  |
Number of employees subject to voluntary options | employee |  |  | 9,000 |  |  |  |  |  |  |  |  | 9,000 |  |
Severance and benefit expenses |  |  | $ 162,000,000 | 350,000,000 | 63,000,000 | 0 | $ 2,000,000 | $ 2,000,000 | $ 6,000,000 | $ 6,000,000 |  | $ 575,000,000 | 16,000,000 | 41,000,000
Impairment of right-of-use assets |  |  |  |  |  |  |  |  |  |  |  | 38,000,000 |  |
Impairments related to cancelled projects |  |  |  |  |  |  |  |  |  |  |  | 56,000,000 |  |
Settlement losses related to defined benefit pension plans |  |  | 41,000,000 | 415,000,000 | 231,000,000 | 0 |  |  |  |  |  | 687,000,000 | 0 | 0
Nonoperating unrealized (gains) losses on investments |  |  | (101,000,000) | (15,000,000) | (9,000,000) | 319,000,000 | (81,000,000) | $ (21,000,000) | $ (34,000,000) | $ (17,000,000) |  | 194,000,000 | (153,000,000) | 5,000,000
Unrealized loss on derivative assets |  |  |  |  |  |  |  |  |  |  |  | 24,000,000 | (13,000,000) |
Expected credit loss allowance recorded |  |  | 0 | $ 0 | $ 0 | $ 697,000,000 |  |  |  |  |  | 697,000,000 | 0 | 0
Write-off of unexercised aircraft purchase |  |  |  |  |  |  |  |  |  |  |  |  | 18,000,000 |
Other miscellaneous impairments |  |  |  |  |  |  |  |  |  |  |  |  | 20,000,000 |
Charges related to contract terminations |  |  |  |  |  |  |  |  |  |  |  |  | 25,000,000 |
Charges for the settlement of certain legal matters |  |  |  |  |  |  |  |  |  |  |  |  | 18,000,000 |
Costs related to the transition of fleet types |  |  |  |  |  |  |  |  |  |  |  |  | 14,000,000 |
Other charges |  |  |  |  |  |  |  |  |  |  |  |  | 2,000,000 |
Gain (loss) on change in market value of equity investments |  |  |  |  |  |  |  |  |  |  |  |  |  | 28,000,000
Gain (loss) due to the change in fair value of derivatives |  |  |  |  |  |  |  |  |  |  |  |  | 13,000,000 |
Fair value adjustments related to aircraft purchased off lease, write-off of unexercised aircraft purchase options and other impairments |  |  |  |  |  |  |  |  |  |  |  |  |  | 66,000,000
One-time termination charge related to engine maintenance service agreements |  |  |  |  |  |  |  |  |  |  |  | 0 | 0 | 64,000,000
Losses due to the change in fair value of derivatives |  |  |  |  |  |  |  |  |  |  |  |  |  | (33,000,000)
COVID-19 [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Special Charges [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Portion of grant recognized as a credit to special charges |  |  |  |  |  |  |  |  |  |  |  | 3,500,000,000 |  |
International Brotherhood of Teamsters |  |  |  |  |  |  |  |  |  |  |  |  |  |
Special Charges [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Severance and benefit expenses |  |  |  |  |  |  |  |  |  |  |  |  | 2,000,000 | 22,000,000
International Brotherhood of Teamsters | Voluntary Early Out Program |  |  |  |  |  |  |  |  |  |  |  |  |  |
Special Charges [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of technicians and related employees electing to voluntarily separate from the Company | employee |  |  |  |  |  |  |  |  |  |  | 1,000 |  |  |
Severance payment per participant |  |  |  |  |  |  |  |  |  |  | $ 100,000 |  |  |
Management |  |  |  |  |  |  |  |  |  |  |  |  |  |
Special Charges [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Severance and benefit expenses |  |  |  |  |  |  |  |  |  |  |  |  | 14,000,000 | 19,000,000
Aircraft Engines |  |  |  |  |  |  |  |  |  |  |  |  |  |
Special Charges [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Tangible asset impairment charges |  |  |  |  |  |  |  |  |  |  |  |  | 43,000,000 |
Hong Kong Routes |  |  |  |  |  |  |  |  |  |  |  |  |  |
Special Charges [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Intangible assets impairment charges |  |  |  |  |  |  |  |  |  |  |  |  | 90,000,000 | $ 206,000,000
Brazil Routes |  |  |  |  |  |  |  |  |  |  |  |  |  |
Special Charges [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Intangible assets impairment charges |  | $ 105,000,000 |  |  |  |  |  |  |  |  |  |  |  |
Azul |  |  |  |  |  |  |  |  |  |  |  |  |  |
Special Charges [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (loss) on equity securities |  |  |  |  |  |  | $ 136,000,000 |  |  |  |  | (180,000,000) |  |
Gain (loss) on change in market value of equity investments |  |  |  |  |  |  |  |  |  |  |  |  | $ 140,000,000 |
Investments Excluding AVH Derivative Assets |  |  |  |  |  |  |  |  |  |  |  |  |  |
Special Charges [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Nonoperating unrealized (gains) losses on investments |  |  |  |  |  |  |  |  |  |  |  | $ 170,000,000 |  |
Boeing 757-200 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Special Charges [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Tangible asset impairment charges |  |  | $ 94,000,000 |  |  |  |  |  |  |  |  |  |  |
Number of planes permanently grounded | plane |  |  | 11 |  |  |  |  |  |  |  |  | 11 |  |
Routes |  |  |  |  |  |  |  |  |  |  |  |  |  |
Special Charges [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Intangible assets impairment charges |  |  |  |  |  |  |  |  |  |  |  | $ 130,000,000 |  |

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