| **Deferred Policy Acquisition Costs (Deferred Policy Acquisition Costs And Asset Reconciliation Including The Amortized Deferred Policy Acquisition Costs) (Details) - USD ($) $ in Millions** | 12 Months Ended |
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| **Deferred Costs [Roll Forward]**                                                                                                                                                              |            |   |   |
| Deferred policy acquisition costs asset at January 1                                                                                                                                           | $ 578           | $ 565 | $ 470 |
| Capitalized deferred policy acquisition costs                                                                                                                                                  | 846             | 827 | 802 |
| Amortized deferred policy acquisition costs                                                                                                                                                    | (829)           | (807) | (758) |
| Amortized shadow deferred policy acquisition costs                                                                                                                                             | 21              | (7) | 51 |
| Deferred policy acquisition costs asset at December 31                                                                                                                                         | 616             | 578 | 565 |
| Property Casualty Insurance Segment [Member]                                                                                                                                                   |            |   |   |
| **Deferred Costs [Roll Forward]**                                                                                                                                                              |            |   |   |
| Deferred policy acquisition costs asset at January 1                                                                                                                                           | 379             | 366 | 337 |
| Capitalized deferred policy acquisition costs                                                                                                                                                  | 801             | 783 | 756 |
| Amortized deferred policy acquisition costs                                                                                                                                                    | (792)           | (770) | (727) |
| Deferred policy acquisition costs asset at December 31                                                                                                                                         | 388             | 379 | 366 |
| Life Insurance Product Line [Member]                                                                                                                                                           |            |   |   |
| **Deferred Costs [Roll Forward]**                                                                                                                                                              |            |   |   |
| Deferred policy acquisition costs asset at January 1                                                                                                                                           | 199             | 199 | 133 |
| Capitalized deferred policy acquisition costs                                                                                                                                                  | 45              | 44 | 46 |
| Amortized deferred policy acquisition costs                                                                                                                                                    | (37)            | (37) | (31) |
| Amortized shadow deferred policy acquisition costs                                                                                                                                             | 21              | (7) | 51 |
| Deferred policy acquisition costs asset at December 31                                                                                                                                         | $ 228           | $ 199 | $ 199 |

| X                                                                                                                                                                                                                        |
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| - Definition
Deferred Costs
+ References
No definition available.
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|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of expense related to deferred policy acquisition costs.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                        |
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| - Definition
Amount of other increase (decrease) to amortization expense of deferred policy acquisition cost (DAC).
+ References
No definition available.
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Net amount of deferred policy acquisition costs capitalized on contracts remaining in force as of the balance sheet date.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Total amount of policy acquisition costs capitalized during the income statement period.
+ References
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