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Income Taxes - Income Tax Provision (Benefit) Differed from Amounts Computed at the Statutory Federal Income Tax Rate and Significant Components (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Sep. 30, 2015
Income Taxes [Line Items] |  |  |  |  |  |
Income tax provision at statutory rate | $ 558 | $ 1,064 |  | $ 1,320 |  |
State income taxes, net of federal income tax benefit | 29 | 30 |  | 38 |  |
Foreign tax rate differential | (84) | (43) |  | 0 |  |
Global intangible low-taxed income | 4 | 0 |  | 0 |  |
Foreign income taxes | 2 | 3 |  | 3 |  |
Nondeductible employee meals | 12 | 17 |  | 16 |  |
Impact of Tax Act | (5) | (179) |  | 0 |  |
Income tax adjustment from AOCI | 0 | 0 |  | 180 |  |
State rate change | 3 | 12 |  | (12) |  |
Valuation allowance | (3) | (16) |  | 20 |  |
Other, net | 13 | 8 |  | (26) |  |
Income tax expense (benefit) | 529 | 896 | [1] | 1,539 | [1] |
Current | 14 | (77) |  | (92) |  |
Deferred | 515 | 973 | [2] | 1,631 | [2] |
Valuation allowance recorded | 59 | 63 |  |  |  |
AOCI |  |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |  |
Income tax adjustment from AOCI |  |  |  | 180 |  |
Valuation allowance recorded |  |  |  |  |  | $ 465
AOCI | Pension and Other Postretirement Liabilities |  |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |  |
Valuation allowance recorded |  |  |  |  |  | 285
AOCI | Designated as Hedging Instrument | Fuel |  |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |  |
Valuation allowance recorded |  |  |  |  |  | $ 180
United Airlines, Inc. |  |  |  |  |  |
Income Taxes [Line Items] |  |  |  |  |  |
Income tax provision at statutory rate | 559 | 1,065 |  | 1,321 |  |
State income taxes, net of federal income tax benefit | 29 | 30 |  | 38 |  |
Foreign tax rate differential | (84) | (43) |  | 0 |  |
Global intangible low-taxed income | 4 | 0 |  | 0 |  |
Foreign income taxes | 2 | 3 |  | 3 |  |
Nondeductible employee meals | 12 | 17 |  | 16 |  |
Impact of Tax Act | (5) | (196) |  | 0 |  |
Income tax adjustment from AOCI | 0 | 0 |  | 180 |  |
State rate change | 3 | 12 |  | (12) |  |
Valuation allowance | (3) | (16) |  | 20 |  |
Other, net | 12 | 7 |  | (25) |  |
Income tax expense (benefit) | 529 | 879 | [3] | 1,541 | [3] |
Current | 14 | (77) |  | (92) |  |
Deferred | 515 | 956 | [4] | $ 1,633 | [4] |
Valuation allowance recorded | $ 59 | $ 63 |  |  |  |
[1] | Amounts adjusted due to the adoption of Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606) and Accounting Standards Update No. 2017-07, Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost. See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[2] | Amounts adjusted due to the adoption of Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606). See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[3] | Amounts adjusted due to the adoption of Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606) and Accounting Standards Update No. 2017-07, Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost. See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[4] | Amounts adjusted due to the adoption of Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606). See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.

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