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Income Taxes - Schedule of Expiration Periods of Deferred Tax Assets (Details) - USD ($) $ in Millions | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
--- | --- | --- | --- | ---
Tax Credit Carryforward [Line Items] |  |  |  |
Tax loss carryforwards | $ 3,159 |  |  |
Tax credit carryforwards | 579 |  |  |
Other | 1,084 |  |  |
Valuation allowance | (2,486) | $ (2,584) | $ (1,940) | $ (1,291)
Deferred tax assets, net | 2,336 | $ 2,503 |  |
Expires within 10 years |  |  |  |
Tax Credit Carryforward [Line Items] |  |  |  |
Tax loss carryforwards | 300 |  |  |
Tax credit carryforwards | 497 |  |  |
Other | 0 |  |  |
Valuation allowance | (752) |  |  |
Deferred tax assets, net | 45 |  |  |
Expires within 11-20 years |  |  |  |
Tax Credit Carryforward [Line Items] |  |  |  |
Tax loss carryforwards | 461 |  |  |
Tax credit carryforwards | 70 |  |  |
Other | 0 |  |  |
Valuation allowance | (287) |  |  |
Deferred tax assets, net | 244 |  |  |
No expiration |  |  |  |
Tax Credit Carryforward [Line Items] |  |  |  |
Tax loss carryforwards | 2,398 |  |  |
Tax credit carryforwards | 12 |  |  |
Other | 64 |  |  |
Valuation allowance | (1,390) |  |  |
Deferred tax assets, net | 1,084 |  |  |
Other(2) |  |  |  |
Tax Credit Carryforward [Line Items] |  |  |  |
Tax loss carryforwards | 0 |  |  |
Tax credit carryforwards | 0 |  |  |
Other | 1,020 |  |  |
Valuation allowance | (57) |  |  |
Deferred tax assets, net | $ 963 |  |  |

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