| **Investments (Components of other-than-temporary impairment losses recognized in earnings) (Details) - USD ($) $ in Millions** | 12 Months Ended |
|---------------------------------------------------------------------------------------------------------------------------------|-----------------|
||
| **Debt Securities, Available-for-sale [Line Items]**                                                                            |            |   |   |
| Total fixed maturity securities available-for-sale                                                                              | $ 44            | $ 21 | $ 13 |
| OTTI losses recognized in earnings                                                                                              | 44              | 21 | 14 |
| Corporate and other bonds                                                                                                       |            |   |   |
| **Debt Securities, Available-for-sale [Line Items]**                                                                            |            |   |   |
| Total fixed maturity securities available-for-sale                                                                              | 33              | 12 | 12 |
| Asset-backed                                                                                                                    |            |   |   |
| **Debt Securities, Available-for-sale [Line Items]**                                                                            |            |   |   |
| Total fixed maturity securities available-for-sale                                                                              | 11              | 9 | 1 |
| Equity securities                                                                                                               |            |   |   |
| **Debt Securities, Available-for-sale [Line Items]**                                                                            |            |   |   |
| OTTI losses recognized in earnings                                                                                              | $ 0             | $ 0 | $ 1 |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of other-than-temporary impairment (OTTI) on investment in debt security, recognized in earnings.
+ References
Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 8A -URI http://asc.fasb.org/extlink&oid=118954083&loc=SL6284422-111562
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The amount of other than temporary impairment (OTTI) losses on equity securities, OTTI related to credit losses on debt securities, and OTTI losses on debt securities when the entity intends to sell the securities or it is more likely than not that the entity will be required to sell the securities before recovery of its amortized cost basis. Additionally, this item includes OTTI losses recognized during the period on investments accounted for under the cost method of accounting.
+ References
No definition available.
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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.
+ Details**Name:**us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                             |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                           |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_FinancialInstrumentAxis=us-gaap_AssetBackedSecuritiesMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                      |
|--------------------------------------------------------------------------------------------------------------------------------------------------------|
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