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Income Taxes - Temporary Differences and Carryforwards Giving Rise to Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Deferred income tax asset (liability): |  |
Federal and state net operating loss ("NOL") carryforwards | $ 2,476 | $ 695
Deferred revenue | 1,409 | 1,287
Employee benefits, including pension, postretirement and medical | 1,103 | 715
Operating lease liabilities | 1,247 | 1,256
Sale leaseback liabilities | 260 | 0
Other | 362 | 165
Less: Valuation allowance | (247) | (58)
Total deferred tax assets | 6,610 | 4,060
Depreciation | (4,789) | (4,011)
Operating lease right-of-use asset | (1,028) | (1,061)
Intangibles | (662) | (724)
Total deferred tax liabilities | (6,479) | (5,796)
Net deferred tax asset | 131 |
Net deferred tax asset (liability) |  | (1,736)
United Airlines, Inc. |  |
Deferred income tax asset (liability): |  |
Federal and state net operating loss ("NOL") carryforwards | 2,448 | 668
Deferred revenue | 1,409 | 1,287
Employee benefits, including pension, postretirement and medical | 1,103 | 715
Operating lease liabilities | 1,247 | 1,256
Sale leaseback liabilities | 260 | 0
Other | 362 | 165
Less: Valuation allowance | (247) | (58)
Total deferred tax assets | 6,582 | 4,033
Depreciation | (4,789) | (4,011)
Operating lease right-of-use asset | (1,028) | (1,061)
Intangibles | (662) | (724)
Total deferred tax liabilities | (6,479) | (5,796)
Net deferred tax asset | $ 103 |
Net deferred tax asset (liability) |  | $ (1,763)

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