| **Investments (Net realized investment gains (losses)) (Details) - USD ($)**                                                        | 3 Months Ended | 9 Months Ended |
|-------------------------------------------------------------------------------------------------------------------------------------|----------------|----------------|
||
| **Fixed maturity securities:**                                                                                                      |           |           |   |   |
| Gross gains                                                                                                                         | $ 12,000,000   | $ 23,000,000   | $ 55,000,000 | $ 94,000,000 |
| Gross losses                                                                                                                        | (49,000,000)   | (134,000,000)  | (141,000,000) | (222,000,000) |
| Net investment gains (losses) on fixed maturity securities                                                                          | (37,000,000)   | (111,000,000)  | (86,000,000) | (128,000,000) |
| Equity securities                                                                                                                   | 2,000,000      | (2,000,000)    | (9,000,000) | (111,000,000) |
| Derivatives                                                                                                                         | 0              | 24,000,000     | 0 | 79,000,000 |
| Mortgage loans                                                                                                                      | (5,000,000)    | (8,000,000)    | (11,000,000) | (8,000,000) |
| Short term investments and other                                                                                                    | 2,000,000      | 1,000,000      | 1,000,000 | 2,000,000 |
| Net investment gains (losses)                                                                                                       | (38,000,000)   | (96,000,000)   | (105,000,000) | (166,000,000) |
| Non-redeemable preferred stock                                                                                                      |           |           |   |   |
| **Fixed maturity securities:**                                                                                                      |           |           |   |   |
| Net investment income (loss) recognized due to the change in fair value of common stock held as of September 30, 2023 and 2022 | $ 2,000,000    | $ (2,000,000)  | $ 2,000,000 | $ (109,000,000) |

| X                                                                                                                                                                                                                                                                                |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Investments And Derivatives, Realized Gain (Loss)
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| X                                                                                                                                                                                                                                                                          |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Realized Gain (Loss) On Short Term Investments
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No definition available.
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| - References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of realized gain on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).
+ References
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of realized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).
+ References
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|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of realized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).
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|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of unrealized and realized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).
+ References
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|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of realized gain (loss) from sale of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).
+ References
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|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The difference between the book value and the sale price of options, swaps, futures, forward contracts, and other derivative instruments. This element refers to the gain (loss) included in earnings.
+ References
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|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of credit loss expense (reversal of expense) for financing receivable.
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