| **Fair Value (Quantitative information about significant unobservable inputs in the fair value measurement of level 3 assets) (Details) - USD ($) $ / shares in Units, $ in Millions** | Dec. 31, 2015 | Dec. 31, 2014 |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------|---------------|
| Fixed maturity securities [Member] | Income Approach Valuation Technique [Member]                                                                                                      |          |          |
| **Fair Value Inputs, Assets, Quantitative Information [Line Items]**                                                                                                                   |          |          |
| Assets, Fair Value Disclosure                                                                                                                                                          | $ 138         | $ 101         |
| Fixed maturity securities [Member] | Income Approach Valuation Technique [Member] | Minimum [Member]                                                                                   |          |          |
| **Fair Value Inputs, Assets, Quantitative Information [Line Items]**                                                                                                                   |          |          |
| fair value inputs, credit risk, counterparty                                                                                                                                           | 0.03          | 0.02          |
| Fixed maturity securities [Member] | Income Approach Valuation Technique [Member] | Maximum [Member]                                                                                   |          |          |
| **Fair Value Inputs, Assets, Quantitative Information [Line Items]**                                                                                                                   |          |          |
| fair value inputs, credit risk, counterparty                                                                                                                                           | 1.84          | 0.13          |
| Fixed maturity securities [Member] | Income Approach Valuation Technique [Member] | Weighted Average [Member]                                                                          |          |          |
| **Fair Value Inputs, Assets, Quantitative Information [Line Items]**                                                                                                                   |          |          |
| fair value inputs, credit risk, counterparty                                                                                                                                           | 0.06          | 0.03          |
| Total equity securities available-for-sale [Member] | Market Approach Valuation Technique [Member]                                                                                     |          |          |
| **Fair Value Inputs, Assets, Quantitative Information [Line Items]**                                                                                                                   |          |          |
| Assets, Fair Value Disclosure                                                                                                                                                          |          | $ 16          |
| Total equity securities available-for-sale [Member] | Market Approach Valuation Technique [Member] | Minimum [Member]                                                                  |          |          |
| **Fair Value Inputs, Assets, Quantitative Information [Line Items]**                                                                                                                   |          |          |
| Private offering price                                                                                                                                                                 |          | $ 12          |
| Total equity securities available-for-sale [Member] | Market Approach Valuation Technique [Member] | Maximum [Member]                                                                  |          |          |
| **Fair Value Inputs, Assets, Quantitative Information [Line Items]**                                                                                                                   |          |          |
| Private offering price                                                                                                                                                                 |          | 4,391         |
| Total equity securities available-for-sale [Member] | Market Approach Valuation Technique [Member] | Weighted Average [Member]                                                         |          |          |
| **Fair Value Inputs, Assets, Quantitative Information [Line Items]**                                                                                                                   |          |          |
| Private offering price                                                                                                                                                                 |          | $ 600         |
| Life settlement contracts, included in Other assets [Member] | Income Approach Valuation Technique [Member]                                                                            |          |          |
| **Fair Value Inputs, Assets, Quantitative Information [Line Items]**                                                                                                                   |          |          |
| Assets, Fair Value Disclosure                                                                                                                                                          | $ 74          | $ 82          |
| Life settlement contracts, included in Other assets [Member] | Income Approach Valuation Technique [Member] | Minimum [Member]                                                         |          |          |
| **Fair Value Inputs, Assets, Quantitative Information [Line Items]**                                                                                                                   |          |          |
| Mortality assumption                                                                                                                                                                   | 55.00%        | 55.00%        |
| Life settlement contracts, included in Other assets [Member] | Income Approach Valuation Technique [Member] | Maximum [Member]                                                         |          |          |
| **Fair Value Inputs, Assets, Quantitative Information [Line Items]**                                                                                                                   |          |          |
| Mortality assumption                                                                                                                                                                   | 1676.00%      | 1676.00%      |
| Life settlement contracts, included in Other assets [Member] | Income Approach Valuation Technique [Member] | Weighted Average [Member]                                                |          |          |
| **Fair Value Inputs, Assets, Quantitative Information [Line Items]**                                                                                                                   |          |          |
| Mortality assumption                                                                                                                                                                   | 164.00%       | 163.00%       |
| Life settlement contracts, included in Other assets [Member] | Income Approach Valuation Technique [Member] | Rate [Member]                                                            |          |          |
| **Fair Value Inputs, Assets, Quantitative Information [Line Items]**                                                                                                                   |          |          |
| Discount rate risk premium                                                                                                                                                             | 9.00%         | 9.00%         |

| X                                                                                                                                                                                                                               |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Discount rate risk premium
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                 |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
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+ References
No definition available.
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| X                                                                                                                                                                                                                     |
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| - Definition
Mortality assumption
+ References
No definition available.
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| X                                                                                                                                                                                                                         |
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| - Definition
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+ 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=36462937&loc=d3e19207-110258
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|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - 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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