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Income Taxes - Additional Disclosures (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2018 | Mar. 31, 2017 | Dec. 31, 2017
Income Tax Contingency [Line Items] |  |  |
Tax Cuts and Jobs Act of 2017, change in tax rate, deferred tax asset, income tax expense (benefit) |  |  | $ (101)
Effective tax rate (as a percent) | (950.00%) | 19.00% |
Tax Cuts and Jobs Act of 2017, income tax expense (benefit) | $ 20 |  |
Accounting Standards Update 2017-05 [Member] |  |  |
Income Tax Contingency [Line Items] |  |  |
Income (loss) attributable to noncontrolling interest, before tax | $ 231 |  |

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