| **Fair Value (Quantitative information about significant unobservable inputs in the fair value measurement of level 3 assets) (Details) - Income Approach Valuation Technique [Member] - USD ($) $ in Millions** | Dec. 31, 2016 | Dec. 31, 2015 |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------|---------------|
| Fixed maturity securities [Member]                                                                                                                                                                               |          |          |
| **Fair Value Inputs, Assets, Quantitative Information [Line Items]**                                                                                                                                             |          |          |
| Assets, Fair Value Disclosure                                                                                                                                                                                    | $ 106         | $ 138         |
| Fixed maturity securities [Member] | Minimum [Member]                                                                                                                                                            |          |          |
| **Fair Value Inputs, Assets, Quantitative Information [Line Items]**                                                                                                                                             |          |          |
| Credit Spread                                                                                                                                                                                                    | 2.00%         | 3.00%         |
| Fixed maturity securities [Member] | Maximum [Member]                                                                                                                                                            |          |          |
| **Fair Value Inputs, Assets, Quantitative Information [Line Items]**                                                                                                                                             |          |          |
| Credit Spread                                                                                                                                                                                                    | 40.00%        | 184.00%       |
| Fixed maturity securities [Member] | Weighted Average [Member]                                                                                                                                                   |          |          |
| **Fair Value Inputs, Assets, Quantitative Information [Line Items]**                                                                                                                                             |          |          |
| Credit Spread                                                                                                                                                                                                    | 4.00%         | 6.00%         |
| Life settlement contracts, included in Other assets [Member]                                                                                                                                                     |          |          |
| **Fair Value Inputs, Assets, Quantitative Information [Line Items]**                                                                                                                                             |          |          |
| Assets, Fair Value Disclosure                                                                                                                                                                                    |          | $ 74          |
| Discount rate risk premium                                                                                                                                                                                       |               | 9.00%         |
| Life settlement contracts, included in Other assets [Member] | Minimum [Member]                                                                                                                                  |          |          |
| **Fair Value Inputs, Assets, Quantitative Information [Line Items]**                                                                                                                                             |          |          |
| Mortality assumption                                                                                                                                                                                             |               | 55.00%        |
| Life settlement contracts, included in Other assets [Member] | Maximum [Member]                                                                                                                                  |          |          |
| **Fair Value Inputs, Assets, Quantitative Information [Line Items]**                                                                                                                                             |          |          |
| Mortality assumption                                                                                                                                                                                             |               | 1676.00%      |
| Life settlement contracts, included in Other assets [Member] | Weighted Average [Member]                                                                                                                         |          |          |
| **Fair Value Inputs, Assets, Quantitative Information [Line Items]**                                                                                                                                             |          |          |
| Mortality assumption                                                                                                                                                                                             |               | 164.00%       |

| X                                                                                                                                                                                                                               |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Discount rate risk premium
+ References
No definition available.
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| X                                                                                                                                                                                                                                                               |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
fair value inputs, credit risk, counterparty
+ References
No definition available.
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| X                                                                                                                                                                                                                     |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Mortality assumption
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258
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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                                                                                                                                                             |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                                     |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                               |
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