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Fair Value (Quantitative information about significant unobservable inputs in the fair value measurement of level 3 assets) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified | Jun. 30, 2013 | Dec. 31, 2012
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Fixed maturity securities [Member] | Income Approach Valuation Technique [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Assets, Fair Value Disclosure | $ 106 | $ 121
Fixed maturity securities [Member] | Income Approach Valuation Technique [Member] | Minimum [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Expected call date | 1.6 | 3.3
Credit spread adjustment |  | 0.02%
Credit spread | 1.95% |
Fixed maturity securities [Member] | Income Approach Valuation Technique [Member] | Maximum [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Expected call date | 3.5 | 5.3
Credit spread adjustment |  | 0.48%
Credit spread | 7.95% |
Fixed maturity securities [Member] | Income Approach Valuation Technique [Member] | Weighted Average [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Expected call date | 3.1 | 4.3
Credit spread adjustment |  | 0.17%
Credit spread | 2.67% |
Fixed maturity securities [Member] | Market approach valuation technique [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Assets, Fair Value Disclosure | 83 | 72
Fixed maturity securities [Member] | Market approach valuation technique [Member] | Minimum [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Private offering price | $ 36.32 | $ 42.39
Fixed maturity securities [Member] | Market approach valuation technique [Member] | Maximum [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Private offering price | $ 113.76 | $ 102.32
Fixed maturity securities [Member] | Market approach valuation technique [Member] | Weighted Average [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Private offering price | $ 101.70 | $ 100.11
Equity securities [Member] | Market approach valuation technique [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Assets, Fair Value Disclosure | 13 | 34
Equity securities [Member] | Market approach valuation technique [Member] | Minimum [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Private offering price | $ 33.73 | $ 4.54
Equity securities [Member] | Market approach valuation technique [Member] | Maximum [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Private offering price | $ 4,017.00 | $ 3,842.00
Equity securities [Member] | Market approach valuation technique [Member] | Weighted Average [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Private offering price | $ 936.89 | $ 571.17
Life settlement contracts [Member] | Income Approach Valuation Technique [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Assets, Fair Value Disclosure | $ 91 | $ 100
Life settlement contracts [Member] | Income Approach Valuation Technique [Member] | Minimum [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Mortality assumption | 69.00% | 69.00%
Life settlement contracts [Member] | Income Approach Valuation Technique [Member] | Maximum [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Mortality assumption | 883.00% | 883.00%
Life settlement contracts [Member] | Income Approach Valuation Technique [Member] | Weighted Average [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Mortality assumption | 209.20% | 208.90%
Life settlement contracts [Member] | Income Approach Valuation Technique [Member] | Rate [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Discount rate risk premium | 9.00% | 9.00%

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- Definition Internally developed credit spread. + References No definition available. + Details
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- Definition Discount rate risk premium + References No definition available. + Details
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- Definition Expected call date in years + References No definition available. + Details
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- Definition Mortality assumption + References No definition available. + Details
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- Definition Private offering price + References No definition available. + Details
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Balance Type: | na
Period Type: | instant

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- Definition This element represents the aggregate of the assets reported on the balance sheet at period end measured at fair value by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. + 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=7578670&loc=d3e19207-110258 + Details
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- Definition The percentage points added to the reference rate to compute the variable rate on the debt instrument. + References No definition available. + Details
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