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Income Taxes - Narrative (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Income Tax [Line Items] |  |  |
Income tax benefit, adjustment |  | $ 4 |
Other income tax disclosures |  |  |
Effect of unrecognized tax benefit on income tax expense | $ 37 | 38 | $ 38
Interest and penalties expense related to unrecognized income tax expense (benefit) | 3 |  | $ 3
Net accrued interest and penalties | 21 | 19 |
Maximum |  |  |
Other income tax disclosures |  |  |
Interest and penalties expense related to unrecognized income tax expense (benefit) |  | $ (1) |
State |  |  |
Other income tax disclosures |  |  |
NOL carryforwards | 1,895 |  |
Deferred income tax asset for State NOL carryforwards | 86 |  |
Federal |  |  |
Other income tax disclosures |  |  |
Deferred tax asset for Federal NOL carryforward | $ 10 |  |

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