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Income Taxes (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2018 | Dec. 31, 2017 | Jun. 30, 2017 | Jun. 30, 2018 | Jun. 30, 2017
Income Tax Disclosure [Abstract] |  |  |  |  |
Effective income tax rate | 165.50% |  | 76.90% | (4.80%) | (181.00%)
Income tax expense (benefit) | $ 144 |  | $ 143 | $ 30 | $ 143
Income (loss) from continuing operations before income taxes | 87 |  | $ 186 | $ (631) | $ (79)
Provisional income tax expense |  | $ 345 |  |  |
Reduction in provisional expense | $ 11 |  |  |  |
Effect of change in enacted tax rate (percentage) | 12.60% |  |  | (1.70%) |

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