v3.19.1

Debt Debt Repurchases (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Debt Instrument, Redemption [Line Items] |  |  |
Gains (Losses) on Extinguishment of Debt | $ 28 | $ (38) | $ (25)
Senior Unsecured Notes 2023 [Member] |  |  |
Debt Instrument, Redemption [Line Items] |  |  |
Debt Instrument, Repurchased Face Amount | 14 |  |
Debt Instrument, Repurchase Amount | 13 |  |
Gains (Losses) on Extinguishment of Debt | 1 |  |
Unsecured Debt [Member] |  |  |
Debt Instrument, Redemption [Line Items] |  |  |
Debt Instrument, Repurchased Face Amount | 390 |  |
Debt Instrument, Repurchase Amount | 355 |  |
Gains (Losses) on Extinguishment of Debt | 35 |  |
Write off of Deferred Debt Issuance Cost | 3 |  |
Senior Unsecured Notes 2024 [Member] |  |  |
Debt Instrument, Redemption [Line Items] |  |  |
Debt Instrument, Repurchased Face Amount | 46 |  |
Debt Instrument, Repurchase Amount | 42 |  |
Gains (Losses) on Extinguishment of Debt | 4 |  |
Senior Unsecured Notes 2025 [Member] |  |  |
Debt Instrument, Redemption [Line Items] |  |  |
Debt Instrument, Repurchased Face Amount | 330 |  |
Debt Instrument, Repurchase Amount | 300 |  |
Gains (Losses) on Extinguishment of Debt | $ 30 |  |

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