| **Deferred Acquisition Costs - Deferred Policy Acquisition Costs and Asset Reconciliation (Detail) - USD ($) $ in Millions** | 3 Months Ended |
|------------------------------------------------------------------------------------------------------------------------------|----------------|
||
| **Movement Analysis of Deferred Policy Acquisition Costs**                                                                   |           |   |
| Deferred policy acquisition costs asset, beginning of period                                                                 | $ 774          | $ 738 |
| Capitalized deferred policy acquisition costs                                                                                | 295            | 270 |
| Amortized deferred policy acquisition costs                                                                                  | (265)          | (246) |
| Shadow deferred policy acquisition costs                                                                                     | 23             | (11) |
| Deferred policy acquisition costs asset, end of period                                                                       | 827            | 751 |
| Consolidated Property and Casualty Insurance Entity                                                                          |           |   |
| **Movement Analysis of Deferred Policy Acquisition Costs**                                                                   |           |   |
| Deferred policy acquisition costs asset, beginning of period                                                                 | 512            | 464 |
| Capitalized deferred policy acquisition costs                                                                                | 280            | 254 |
| Amortized deferred policy acquisition costs                                                                                  | (256)          | (233) |
| Deferred policy acquisition costs asset, end of period                                                                       | 536            | 485 |
| Life Insurance Segment                                                                                                       |           |   |
| **Movement Analysis of Deferred Policy Acquisition Costs**                                                                   |           |   |
| Deferred policy acquisition costs asset, beginning of period                                                                 | 262            | 274 |
| Capitalized deferred policy acquisition costs                                                                                | 15             | 16 |
| Amortized deferred policy acquisition costs                                                                                  | (9)            | (13) |
| Shadow deferred policy acquisition costs                                                                                     | 23             | (11) |
| Deferred policy acquisition costs asset, end of period                                                                       | $ 291          | $ 266 |

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| - Definition
Amount of amortization expense (reversal of expense) for deferred policy acquisition costs.
+ References
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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
Amount of deferred policy acquisition cost capitalized on contract remaining in force.
+ References
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|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of deferred policy acquisition cost capitalized.
+ References
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| - Definition
A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.
+ References
No definition available.
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