| **General (Adoption of Updated Guidance) (Details) - USD ($) $ in Millions**     | Jun. 30, 2019 | Jan. 01, 2019 | Dec. 31, 2018 |
|----------------------------------------------------------------------------------|---------------|---------------|---------------|
| **New Accounting Pronouncements or Change in Accounting Principle [Line Items]** |          |          |          |
| Property and equipment at cost (less accumulated depreciation)                   | $ 302         | $ 326         | $ 324         |
| Other assets                                                                     | 1,749         | 1,445         | 1,208         |
| Other liabilities                                                                | 3,689         | 3,328         | $ 3,089       |
| Adjustments Due to Adoption of Topic 842                                         |          |          |          |
| **New Accounting Pronouncements or Change in Accounting Principle [Line Items]** |          |          |          |
| Property and equipment at cost (less accumulated depreciation)                   |          | 2             |          |
| Other assets                                                                     | $ (75)        | 237           |          |
| Other liabilities                                                                |          | $ 239         |          |

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Amount of assets classified as other.
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| - Definition
Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.
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