| **Revenue and Interest Recognized in Income (Details) - Life policy reserves: - USD ($) $ in Millions** | 3 Months Ended | 9 Months Ended |
|---------------------------------------------------------------------------------------------------------|----------------|----------------|
||
| **Liability for Future Policy Benefit, Activity [Line Items]**                                          |           |           |   |   |
| Gross premiums                                                                                          | $ 87           | $ 85           | $ 262 | $ 256 |
| Interest accretion                                                                                      | 18             | 18             | 55 | 53 |
| Term Life Insurance                                                                                     |           |           |   |   |
| **Liability for Future Policy Benefit, Activity [Line Items]**                                          |           |           |   |   |
| Gross premiums                                                                                          | 72             | 71             | 221 | 217 |
| Interest accretion                                                                                      | 12             | 13             | 38 | 37 |
| Whole Life Insurance                                                                                    |           |           |   |   |
| **Liability for Future Policy Benefit, Activity [Line Items]**                                          |           |           |   |   |
| Gross premiums                                                                                          | 15             | 14             | 41 | 39 |
| Interest accretion                                                                                      | $ 6            | $ 5            | $ 17 | $ 16 |

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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.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of gross premium income recognized for liability for future policy benefit.
+ References
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|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of interest expense recognized for liability for future policy benefit.
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| X                                                                                                                                                 |
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