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Reinsurance (Reinsurance Recoverable by Category and Listing of Largest Reinsurers) (Details) - USD ($) $ in Millions | Dec. 31, 2018 | Dec. 31, 2017
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Ceded Credit Risk [Line Items] |  |
Gross reinsurance recoverable | $ 16,316 |
Provision | $ 323 | $ 321
% of Gross | 2.00% |
Largest reinsurers |  |
Ceded Credit Risk [Line Items] |  |
Gross reinsurance recoverable | $ 6,578 |
Provision | $ 70 |
% of Gross | 1.10% |
Other reinsurers balances rated A- or better |  |
Ceded Credit Risk [Line Items] |  |
Gross reinsurance recoverable | $ 5,339 |
Provision | $ 63 |
% of Gross | 1.20% |
Other reinsurers balances with ratings lower than A- or not rated |  |
Ceded Credit Risk [Line Items] |  |
Gross reinsurance recoverable | $ 558 |
Provision | $ 68 |
% of Gross | 12.20% |
Other pools and government agencies |  |
Ceded Credit Risk [Line Items] |  |
Gross reinsurance recoverable | $ 429 |
Provision | $ 16 |
% of Gross | 3.70% |
Structured settlements |  |
Ceded Credit Risk [Line Items] |  |
Gross reinsurance recoverable | $ 548 |
Provision | $ 18 |
% of Gross | 3.30% |
Other captives |  |
Ceded Credit Risk [Line Items] |  |
Gross reinsurance recoverable | $ 2,590 |
Provision | $ 16 |
% of Gross | 0.60% |
Other |  |
Ceded Credit Risk [Line Items] |  |
Gross reinsurance recoverable | $ 274 |
Provision | $ 72 |
% of Gross | 26.30% |

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- Definition Allowance For Reinsurance Recoverable, Percentage + References No definition available. + Details
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Balance Type: | na
Period Type: | instant

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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. + Details
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- Definition Amount of valuation allowance for reinsurance recoverables. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, premium paid, policy benefits and policy reserves. + References No definition available. + Details
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Data Type: | xbrli:monetaryItemType
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Period Type: | instant

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- Definition Amount before valuation allowance recoverable under reinsurance contracts. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, premium paid, policy benefits and policy reserves. + References No definition available. + Details
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- Details
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Namespace Prefix: |
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- Details
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- Details
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- Details
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