| **Benefit Plans (Estimated Future Minimum Benefit Payments to Participants) (Details) $ in Millions** | Dec. 31, 2018 USD ($) |
|-------------------------------------------------------------------------------------------------------|-----------------------|
| Pension Benefits                                                                                      |                  |
| **Defined Benefit Plan Disclosure [Line Items]**                                                      |                  |
| 2019                                                                                                  | $ 175                 |
| 2020                                                                                                  | 174                   |
| 2021                                                                                                  | 175                   |
| 2022                                                                                                  | 177                   |
| 2023                                                                                                  | 177                   |
| 2024-2028                                                                                             | 850                   |
| Postretirement Benefits                                                                               |                  |
| **Defined Benefit Plan Disclosure [Line Items]**                                                      |                  |
| 2019                                                                                                  | 2                     |
| 2020                                                                                                  | 2                     |
| 2021                                                                                                  | 1                     |
| 2022                                                                                                  | 1                     |
| 2023                                                                                                  | 1                     |
| 2024-2028                                                                                             | $ 2                   |

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| - Definition
Amount of benefits for defined benefit plan expected to be paid in five fiscal years after fifth fiscal year following latest fiscal year.
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Amount of benefits for defined benefit plan expected to be paid in next fiscal year following latest fiscal year.
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Amount of benefits for defined benefit plan expected to be paid in fifth fiscal year following latest fiscal year.
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Amount of benefits for defined benefit plan expected to be paid in fourth fiscal year following latest fiscal year.
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Amount of benefits for defined benefit plan expected to be paid in third fiscal year following latest fiscal year.
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Amount of benefits for defined benefit plan expected to be paid in second fiscal year following latest fiscal year.
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