| **Investments (Credit Quality Indicator) (Details) - Mortgage loans $ in Millions** | Mar. 31, 2020 USD ($) |
|-------------------------------------------------------------------------------------|-----------------------|
| **Financing Receivable, Credit Quality Indicator [Line Items]**                     |                  |
| 2020                                                                                | $ 60                  |
| 2019                                                                                | 297                   |
| 2018                                                                                | 115                   |
| 2017                                                                                | 219                   |
| 2016                                                                                | 85                    |
| Prior                                                                               | 265                   |
| Total                                                                               | 1,041                 |
| DSCR ≥1.6x | LTV less than 55%                                                |                  |
| **Financing Receivable, Credit Quality Indicator [Line Items]**                     |                  |
| 2020                                                                                | 60                    |
| 2019                                                                                | 32                    |
| 2018                                                                                | 19                    |
| 2017                                                                                | 92                    |
| 2016                                                                                | 41                    |
| Prior                                                                               | 130                   |
| Total                                                                               | 374                   |
| DSCR ≥1.6x | LTV 55% to 65%                                                   |                  |
| **Financing Receivable, Credit Quality Indicator [Line Items]**                     |                  |
| 2020                                                                                | 0                     |
| 2019                                                                                | 32                    |
| 2018                                                                                | 29                    |
| 2017                                                                                | 55                    |
| 2016                                                                                | 4                     |
| Prior                                                                               | 0                     |
| Total                                                                               | 120                   |
| 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                                                                               | 0                     |
| Total                                                                               | 5                     |
| DSCR 1.2x - 1.6x | LTV less than 55%                                                |                  |
| **Financing Receivable, Credit Quality Indicator [Line Items]**                     |                  |
| 2020                                                                                | 0                     |
| 2019                                                                                | 33                    |
| 2018                                                                                | 10                    |
| 2017                                                                                | 13                    |
| 2016                                                                                | 16                    |
| Prior                                                                               | 126                   |
| Total                                                                               | 198                   |
| DSCR 1.2x - 1.6x | LTV 55% to 65%                                                   |                  |
| **Financing Receivable, Credit Quality Indicator [Line Items]**                     |                  |
| 2020                                                                                | 0                     |
| 2019                                                                                | 73                    |
| 2018                                                                                | 32                    |
| 2017                                                                                | 32                    |
| 2016                                                                                | 0                     |
| Prior                                                                               | 0                     |
| Total                                                                               | 137                   |
| DSCR 1.2x - 1.6x | LTV greater than 65%                                             |                  |
| **Financing Receivable, Credit Quality Indicator [Line Items]**                     |                  |
| 2020                                                                                | 0                     |
| 2019                                                                                | 85                    |
| 2018                                                                                | 0                     |
| 2017                                                                                | 0                     |
| 2016                                                                                | 0                     |
| Prior                                                                               | 0                     |
| Total                                                                               | 85                    |
| DSCR ≤1.2 | LTV less than 55%                                                 |                  |
| **Financing Receivable, Credit Quality Indicator [Line Items]**                     |                  |
| 2020                                                                                | 0                     |
| 2019                                                                                | 1                     |
| 2018                                                                                | 11                    |
| 2017                                                                                | 27                    |
| 2016                                                                                | 0                     |
| Prior                                                                               | 9                     |
| Total                                                                               | 48                    |
| 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                                                                                | 22                    |
| 2018                                                                                | 0                     |
| 2017                                                                                | 0                     |
| 2016                                                                                | 24                    |
| Prior                                                                               | 0                     |
| Total                                                                               | $ 46                  |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of financing receivable originated five or more years prior to latest fiscal year.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of financing receivable originated four years prior to latest fiscal year.
+ References
Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 55 -Paragraph 79 -URI http://asc.fasb.org/extlink&oid=118955255&loc=SL82922352-210448Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=119407570&loc=SL82919232-210447
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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 latest fiscal year.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of financing receivable originated three years prior to latest fiscal year.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of financing receivable originated two years prior to latest 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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| X                                                                                                                                                                          |
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