| **General (Narrative) (Details) - USD ($) $ in Millions**                        | Mar. 31, 2019 | Jan. 01, 2019 | Dec. 31, 2018 |
|----------------------------------------------------------------------------------|---------------|---------------|---------------|
| **New Accounting Pronouncements or Change in Accounting Principle [Line Items]** |          |          |          |
| Other assets                                                                     | $ (1,579)     | $ (1,445)     | $ (1,208)     |
| CNAF Consolidated | Loews                                                        |          |          |          |
| **New Accounting Pronouncements or Change in Accounting Principle [Line Items]** |          |          |          |
| Noncontrolling interest, ownership percentage by parent                          | 89.00%        |          |          |
| Adjustments Due to Adoption of Topic 842                                         |          |          |          |
| **New Accounting Pronouncements or Change in Accounting Principle [Line Items]** |          |          |          |
| Other assets                                                                     | $ 75          | $ (237)       |          |

| X                                                                                                                                                                                                                                                                                                                         |
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The parent entity's interest in net assets of the subsidiary, expressed as a percentage.
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.
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| - Definition
Amount of assets classified as other.
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| X                                                                                                                                    |
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| X                                                                                                                           |
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