| **Investments (Credit Quality Indicator) (Details) - Mortgage loans $ in Millions** | Sep. 30, 2020 USD ($) |
|-------------------------------------------------------------------------------------|-----------------------|
| **Financing Receivable, Credit Quality Indicator [Line Items]**                     |                  |
| 2020                                                                                | $ 143                 |
| 2019                                                                                | 296                   |
| 2018                                                                                | 104                   |
| 2017                                                                                | 222                   |
| 2016                                                                                | 85                    |
| Prior                                                                               | 259                   |
| Total                                                                               | 1,109                 |
| DSCR ≥1.6x | LTV less than 55%                                                |                  |
| **Financing Receivable, Credit Quality Indicator [Line Items]**                     |                  |
| 2020                                                                                | 75                    |
| 2019                                                                                | 33                    |
| 2018                                                                                | 19                    |
| 2017                                                                                | 85                    |
| 2016                                                                                | 33                    |
| Prior                                                                               | 161                   |
| Total                                                                               | 406                   |
| DSCR ≥1.6x | LTV 55% to 65%                                                   |                  |
| **Financing Receivable, Credit Quality Indicator [Line Items]**                     |                  |
| 2020                                                                                | 0                     |
| 2019                                                                                | 33                    |
| 2018                                                                                | 29                    |
| 2017                                                                                | 55                    |
| 2016                                                                                | 12                    |
| Prior                                                                               | 0                     |
| Total                                                                               | 129                   |
| DSCR ≥1.6x | LTV greater than 65%                                             |                  |
| **Financing Receivable, Credit Quality Indicator [Line Items]**                     |                  |
| 2020                                                                                | 0                     |
| 2019                                                                                | 5                     |
| 2018                                                                                | 0                     |
| 2017                                                                                | 0                     |
| 2016                                                                                | 0                     |
| Prior                                                                               | 12                    |
| Total                                                                               | 17                    |
| DSCR 1.2x - 1.6x | LTV less than 55%                                                |                  |
| **Financing Receivable, Credit Quality Indicator [Line Items]**                     |                  |
| 2020                                                                                | 0                     |
| 2019                                                                                | 31                    |
| 2018                                                                                | 10                    |
| 2017                                                                                | 13                    |
| 2016                                                                                | 16                    |
| Prior                                                                               | 79                    |
| Total                                                                               | 149                   |
| DSCR 1.2x - 1.6x | LTV 55% to 65%                                                   |                  |
| **Financing Receivable, Credit Quality Indicator [Line Items]**                     |                  |
| 2020                                                                                | 20                    |
| 2019                                                                                | 54                    |
| 2018                                                                                | 32                    |
| 2017                                                                                | 24                    |
| 2016                                                                                | 0                     |
| Prior                                                                               | 0                     |
| Total                                                                               | 130                   |
| DSCR 1.2x - 1.6x | LTV greater than 65%                                             |                  |
| **Financing Receivable, Credit Quality Indicator [Line Items]**                     |                  |
| 2020                                                                                | 48                    |
| 2019                                                                                | 103                   |
| 2018                                                                                | 0                     |
| 2017                                                                                | 0                     |
| 2016                                                                                | 0                     |
| Prior                                                                               | 0                     |
| Total                                                                               | 151                   |
| DSCR ≤1.2 | LTV less than 55%                                                 |                  |
| **Financing Receivable, Credit Quality Indicator [Line Items]**                     |                  |
| 2020                                                                                | 0                     |
| 2019                                                                                | 0                     |
| 2018                                                                                | 0                     |
| 2017                                                                                | 0                     |
| 2016                                                                                | 0                     |
| Prior                                                                               | 0                     |
| Total                                                                               | 0                     |
| DSCR ≤1.2 | LTV 55% to 65%                                                    |                  |
| **Financing Receivable, Credit Quality Indicator [Line Items]**                     |                  |
| 2020                                                                                | 0                     |
| 2019                                                                                | 14                    |
| 2018                                                                                | 14                    |
| 2017                                                                                | 0                     |
| 2016                                                                                | 0                     |
| Prior                                                                               | 0                     |
| Total                                                                               | 28                    |
| DSCR ≤1.2 | LTV greater than 65%                                              |                  |
| **Financing Receivable, Credit Quality Indicator [Line Items]**                     |                  |
| 2020                                                                                | 0                     |
| 2019                                                                                | 23                    |
| 2018                                                                                | 0                     |
| 2017                                                                                | 45                    |
| 2016                                                                                | 24                    |
| Prior                                                                               | 7                     |
| Total                                                                               | $ 99                  |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of financing receivable originated more than five years prior to current fiscal year.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of financing receivable originated four years prior to current fiscal year.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of financing receivable originated in current fiscal year.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of financing receivable originated in fiscal year prior to current fiscal year.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of financing receivable originated three years prior to current fiscal year.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of financing receivable originated two years prior to current fiscal year.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - 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
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount, before allowance for credit loss, of financing receivable.
+ References
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| X                                                                                                                                               |
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| X                                                                                                                                                                             |
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| X                                                                                                                                                           |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                              |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                              |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                                      |
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