| **General (Narrative) (Details) - USD ($) $ in Millions**                                                               | 3 Months Ended                               |         |
|-------------------------------------------------------------------------------------------------------------------------|----------------------------------------------|---------|
||
| **New Accounting Pronouncements or Change in Accounting Principle [Line Items]**                                        |                                         |    |
| Accounting Standards Update [Extensible Enumeration]                                                                    | Accounting Standards Update 2018-12 [Member] |    |
| Minimum | Pro Forma | Accumulated Other Comprehensive (Loss) Income | Cumulative Effect, Period of Adoption, Adjustment |                                         |    |
| **New Accounting Pronouncements or Change in Accounting Principle [Line Items]**                                        |                                         |    |
| Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest                                         |                                         | $ 2,200 |
| Maximum | Pro Forma | Accumulated Other Comprehensive (Loss) Income | Cumulative Effect, Period of Adoption, Adjustment |                                         |    |
| **New Accounting Pronouncements or Change in Accounting Principle [Line Items]**                                        |                                         |    |
| Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest                                         |                                         | $ 2,500 |
| CNAF Consolidated | Loews                                                                                               |                                         |    |
| **New Accounting Pronouncements or Change in Accounting Principle [Line Items]**                                        |                                         |    |
| Noncontrolling interest, ownership percentage by parent (as a percent)                                                  | 89.60%                                       |    |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      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| - Definition
Indicates amendment to accounting standards.
+ References
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| - Definition
The parent entity's interest in net assets of the subsidiary, expressed as a percentage.
+ References
No definition available.
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| - Definition
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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No definition available.
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| - Definition
Amount of stockholders' equity (deficit), net of receivables from officers, directors, owners, and affiliates of the entity, attributable to both the parent and noncontrolling interests. Amount excludes temporary equity. Alternate caption for the concept is permanent equity.
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