| **Supplementary Insurance Information (Details) (USD $)In Millions, unless otherwise specified** | 12 Months Ended                                                                                                                                                                                                                           |
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| **Supplementary Insurance Information, by Segment**                                              |                                                                                                                                                                                                                                      |   |   |
| Deferred policy acquisition costs                                                                | $ 578us-gaap_SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts                                                                                                                                                              | $ 565us-gaap_SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts | $ 470us-gaap_SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts |
| Gross future policy benefits, losses, claims and expense losses                                  | 6,957us-gaap_SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves                                                                                                                          | 6,682us-gaap_SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves | 6,510us-gaap_SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves |
| Gross unearned premium                                                                           | 2,082us-gaap_SupplementaryInsuranceInformationUnearnedPremiums                                                                                                                                                                            | 1,976us-gaap_SupplementaryInsuranceInformationUnearnedPremiums | 1,792us-gaap_SupplementaryInsuranceInformationUnearnedPremiums |
| Other policy claims and benefits payable                                                         | 25us-gaap_SupplementaryInsuranceInformationOtherPolicyClaimsAndBenefitsPayable                                                                                                                                                            | 19us-gaap_SupplementaryInsuranceInformationOtherPolicyClaimsAndBenefitsPayable | 15us-gaap_SupplementaryInsuranceInformationOtherPolicyClaimsAndBenefitsPayable |
| Earned premiums                                                                                  | 4,243us-gaap_SupplementaryInsuranceInformationPremiumRevenue                                                                                                                                                                              | 3,902us-gaap_SupplementaryInsuranceInformationPremiumRevenue | 3,522us-gaap_SupplementaryInsuranceInformationPremiumRevenue |
| Investment income, net of expenses                                                               | 502us-gaap_SupplementaryInsuranceInformationNetInvestmentIncome                                                                                                                                                                           | 488us-gaap_SupplementaryInsuranceInformationNetInvestmentIncome | 488us-gaap_SupplementaryInsuranceInformationNetInvestmentIncome |
| Benefits, claims losses and settlement expense                                                   | 2,856us-gaap_SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense                                                                                                                                                    | 2,505us-gaap_SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense | 2,322us-gaap_SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense |
| Amortization of deferred policy acquisition costs                                                | 807us-gaap_SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts                                                                                                                                                  | 758us-gaap_SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts | 707us-gaap_SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts |
| Underwriting, acquisition and insurance expenses                                                 | 494us-gaap_SupplementaryInsuranceInformationOtherOperatingExpense                                                                                                                                                                         | 485us-gaap_SupplementaryInsuranceInformationOtherOperatingExpense | 448us-gaap_SupplementaryInsuranceInformationOtherOperatingExpense |
| Net written premiums                                                                             | 4,146us-gaap_SupplementaryInsuranceInformationPremiumsWritten                                                                                                                                                                             | 3,895us-gaap_SupplementaryInsuranceInformationPremiumsWritten | 3,485us-gaap_SupplementaryInsuranceInformationPremiumsWritten |
| Commercial Insurance                                                                             |                                                                                                                                                                                                                                      |   |   |
| **Supplementary Insurance Information, by Segment**                                              |                                                                                                                                                                                                                                      |   |   |
| Deferred policy acquisition costs                                                                | 257us-gaap_SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyCommercialInsuranceProductLineMember                                       | 251us-gaap_SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyCommercialInsuranceProductLineMember | 235us-gaap_SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyCommercialInsuranceProductLineMember |
| Gross future policy benefits, losses, claims and expense losses                                  | 3,797us-gaap_SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyCommercialInsuranceProductLineMember | 3,667us-gaap_SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyCommercialInsuranceProductLineMember | 3,645us-gaap_SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyCommercialInsuranceProductLineMember |
| Gross unearned premium                                                                           | 1,441us-gaap_SupplementaryInsuranceInformationUnearnedPremiums/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyCommercialInsuranceProductLineMember                                                   | 1,372us-gaap_SupplementaryInsuranceInformationUnearnedPremiums/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyCommercialInsuranceProductLineMember | 1,246us-gaap_SupplementaryInsuranceInformationUnearnedPremiums/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyCommercialInsuranceProductLineMember |
| Earned premiums                                                                                  | 2,856us-gaap_SupplementaryInsuranceInformationPremiumRevenue/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyCommercialInsuranceProductLineMember                                                     | 2,636us-gaap_SupplementaryInsuranceInformationPremiumRevenue/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyCommercialInsuranceProductLineMember | 2,383us-gaap_SupplementaryInsuranceInformationPremiumRevenue/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyCommercialInsuranceProductLineMember |
| Benefits, claims losses and settlement expense                                                   | 1,812us-gaap_SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyCommercialInsuranceProductLineMember                           | 1,596us-gaap_SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyCommercialInsuranceProductLineMember | 1,420us-gaap_SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyCommercialInsuranceProductLineMember |
| Amortization of deferred policy acquisition costs                                                | 537us-gaap_SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyCommercialInsuranceProductLineMember                         | 514us-gaap_SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyCommercialInsuranceProductLineMember | 462us-gaap_SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyCommercialInsuranceProductLineMember |
| Underwriting, acquisition and insurance expenses                                                 | 365us-gaap_SupplementaryInsuranceInformationOtherOperatingExpense/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyCommercialInsuranceProductLineMember                                                | 343us-gaap_SupplementaryInsuranceInformationOtherOperatingExpense/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyCommercialInsuranceProductLineMember | 324us-gaap_SupplementaryInsuranceInformationOtherOperatingExpense/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyCommercialInsuranceProductLineMember |
| Net written premiums                                                                             | 2,922us-gaap_SupplementaryInsuranceInformationPremiumsWritten/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyCommercialInsuranceProductLineMember                                                    | 2,760us-gaap_SupplementaryInsuranceInformationPremiumsWritten/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyCommercialInsuranceProductLineMember | 2,459us-gaap_SupplementaryInsuranceInformationPremiumsWritten/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyCommercialInsuranceProductLineMember |
| Personal Insurance                                                                               |                                                                                                                                                                                                                                      |   |   |
| **Supplementary Insurance Information, by Segment**                                              |                                                                                                                                                                                                                                      |   |   |
| Deferred policy acquisition costs                                                                | 108us-gaap_SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyPersonalInsuranceProductLineMember                                         | 104us-gaap_SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyPersonalInsuranceProductLineMember | 93us-gaap_SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyPersonalInsuranceProductLineMember |
| Gross future policy benefits, losses, claims and expense losses                                  | 439us-gaap_SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyPersonalInsuranceProductLineMember     | 417us-gaap_SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyPersonalInsuranceProductLineMember | 398us-gaap_SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyPersonalInsuranceProductLineMember |
| Gross unearned premium                                                                           | 562us-gaap_SupplementaryInsuranceInformationUnearnedPremiums/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyPersonalInsuranceProductLineMember                                                       | 535us-gaap_SupplementaryInsuranceInformationUnearnedPremiums/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyPersonalInsuranceProductLineMember | 490us-gaap_SupplementaryInsuranceInformationUnearnedPremiums/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyPersonalInsuranceProductLineMember |
| Earned premiums                                                                                  | 1,041us-gaap_SupplementaryInsuranceInformationPremiumRevenue/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyPersonalInsuranceProductLineMember                                                       | 961us-gaap_SupplementaryInsuranceInformationPremiumRevenue/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyPersonalInsuranceProductLineMember | 868us-gaap_SupplementaryInsuranceInformationPremiumRevenue/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyPersonalInsuranceProductLineMember |
| Benefits, claims losses and settlement expense                                                   | 740us-gaap_SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyPersonalInsuranceProductLineMember                               | 639us-gaap_SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyPersonalInsuranceProductLineMember | 652us-gaap_SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyPersonalInsuranceProductLineMember |
| Amortization of deferred policy acquisition costs                                                | 209us-gaap_SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyPersonalInsuranceProductLineMember                           | 192us-gaap_SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyPersonalInsuranceProductLineMember | 183us-gaap_SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyPersonalInsuranceProductLineMember |
| Underwriting, acquisition and insurance expenses                                                 | 84us-gaap_SupplementaryInsuranceInformationOtherOperatingExpense/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyPersonalInsuranceProductLineMember                                                   | 98us-gaap_SupplementaryInsuranceInformationOtherOperatingExpense/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyPersonalInsuranceProductLineMember | 78us-gaap_SupplementaryInsuranceInformationOtherOperatingExpense/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyPersonalInsuranceProductLineMember |
| Net written premiums                                                                             | 1,068us-gaap_SupplementaryInsuranceInformationPremiumsWritten/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyPersonalInsuranceProductLineMember                                                      | 1,005us-gaap_SupplementaryInsuranceInformationPremiumsWritten/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyPersonalInsuranceProductLineMember | 918us-gaap_SupplementaryInsuranceInformationPremiumsWritten/ cinf_SegmentReportingInformationBySecondarySegmentAxis= us-gaap_PropertyAndCasualtyPersonalInsuranceProductLineMember |
| Excess And Surplus Lines Insurance                                                               |                                                                                                                                                                                                                                      |   |   |
| **Supplementary Insurance Information, by Segment**                                              |                                                                                                                                                                                                                                      |   |   |
| Deferred policy acquisition costs                                                                | 14us-gaap_SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts/ cinf_SegmentReportingInformationBySecondarySegmentAxis= cinf_ExcessAndSurplusLinesInsuranceMember                                                              | 11us-gaap_SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts/ cinf_SegmentReportingInformationBySecondarySegmentAxis= cinf_ExcessAndSurplusLinesInsuranceMember | 9us-gaap_SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts/ cinf_SegmentReportingInformationBySecondarySegmentAxis= cinf_ExcessAndSurplusLinesInsuranceMember |
| Gross future policy benefits, losses, claims and expense losses                                  | 202us-gaap_SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves/ cinf_SegmentReportingInformationBySecondarySegmentAxis= cinf_ExcessAndSurplusLinesInsuranceMember                         | 157us-gaap_SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves/ cinf_SegmentReportingInformationBySecondarySegmentAxis= cinf_ExcessAndSurplusLinesInsuranceMember | 126us-gaap_SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves/ cinf_SegmentReportingInformationBySecondarySegmentAxis= cinf_ExcessAndSurplusLinesInsuranceMember |
| Gross unearned premium                                                                           | 78us-gaap_SupplementaryInsuranceInformationUnearnedPremiums/ cinf_SegmentReportingInformationBySecondarySegmentAxis= cinf_ExcessAndSurplusLinesInsuranceMember                                                                            | 67us-gaap_SupplementaryInsuranceInformationUnearnedPremiums/ cinf_SegmentReportingInformationBySecondarySegmentAxis= cinf_ExcessAndSurplusLinesInsuranceMember | 54us-gaap_SupplementaryInsuranceInformationUnearnedPremiums/ cinf_SegmentReportingInformationBySecondarySegmentAxis= cinf_ExcessAndSurplusLinesInsuranceMember |
| Earned premiums                                                                                  | 148us-gaap_SupplementaryInsuranceInformationPremiumRevenue/ cinf_SegmentReportingInformationBySecondarySegmentAxis= cinf_ExcessAndSurplusLinesInsuranceMember                                                                             | 116us-gaap_SupplementaryInsuranceInformationPremiumRevenue/ cinf_SegmentReportingInformationBySecondarySegmentAxis= cinf_ExcessAndSurplusLinesInsuranceMember | 93us-gaap_SupplementaryInsuranceInformationPremiumRevenue/ cinf_SegmentReportingInformationBySecondarySegmentAxis= cinf_ExcessAndSurplusLinesInsuranceMember |
| Benefits, claims losses and settlement expense                                                   | 75us-gaap_SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense/ cinf_SegmentReportingInformationBySecondarySegmentAxis= cinf_ExcessAndSurplusLinesInsuranceMember                                                    | 66us-gaap_SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense/ cinf_SegmentReportingInformationBySecondarySegmentAxis= cinf_ExcessAndSurplusLinesInsuranceMember | 65us-gaap_SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense/ cinf_SegmentReportingInformationBySecondarySegmentAxis= cinf_ExcessAndSurplusLinesInsuranceMember |
| Amortization of deferred policy acquisition costs                                                | 24us-gaap_SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts/ cinf_SegmentReportingInformationBySecondarySegmentAxis= cinf_ExcessAndSurplusLinesInsuranceMember                                                | 21us-gaap_SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts/ cinf_SegmentReportingInformationBySecondarySegmentAxis= cinf_ExcessAndSurplusLinesInsuranceMember | 17us-gaap_SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts/ cinf_SegmentReportingInformationBySecondarySegmentAxis= cinf_ExcessAndSurplusLinesInsuranceMember |
| Underwriting, acquisition and insurance expenses                                                 | 19us-gaap_SupplementaryInsuranceInformationOtherOperatingExpense/ cinf_SegmentReportingInformationBySecondarySegmentAxis= cinf_ExcessAndSurplusLinesInsuranceMember                                                                       | 15us-gaap_SupplementaryInsuranceInformationOtherOperatingExpense/ cinf_SegmentReportingInformationBySecondarySegmentAxis= cinf_ExcessAndSurplusLinesInsuranceMember | 12us-gaap_SupplementaryInsuranceInformationOtherOperatingExpense/ cinf_SegmentReportingInformationBySecondarySegmentAxis= cinf_ExcessAndSurplusLinesInsuranceMember |
| Net written premiums                                                                             | 153us-gaap_SupplementaryInsuranceInformationPremiumsWritten/ cinf_SegmentReportingInformationBySecondarySegmentAxis= cinf_ExcessAndSurplusLinesInsuranceMember                                                                            | 128us-gaap_SupplementaryInsuranceInformationPremiumsWritten/ cinf_SegmentReportingInformationBySecondarySegmentAxis= cinf_ExcessAndSurplusLinesInsuranceMember | 105us-gaap_SupplementaryInsuranceInformationPremiumsWritten/ cinf_SegmentReportingInformationBySecondarySegmentAxis= cinf_ExcessAndSurplusLinesInsuranceMember |
| Property, Liability and Casualty Insurance Product Line [Member]                                 |                                                                                                                                                                                                                                      |   |   |
| **Supplementary Insurance Information, by Segment**                                              |                                                                                                                                                                                                                                      |   |   |
| Deferred policy acquisition costs                                                                | 379us-gaap_SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember                                                             | 366us-gaap_SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember | 337us-gaap_SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember |
| Gross future policy benefits, losses, claims and expense losses                                  | 4,438us-gaap_SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember                       | 4,241us-gaap_SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember | 4,169us-gaap_SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember |
| Gross unearned premium                                                                           | 2,081us-gaap_SupplementaryInsuranceInformationUnearnedPremiums/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember                                                                         | 1,974us-gaap_SupplementaryInsuranceInformationUnearnedPremiums/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember | 1,790us-gaap_SupplementaryInsuranceInformationUnearnedPremiums/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember |
| Earned premiums                                                                                  | 4,045us-gaap_SupplementaryInsuranceInformationPremiumRevenue/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember                                                                           | 3,713us-gaap_SupplementaryInsuranceInformationPremiumRevenue/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember | 3,344us-gaap_SupplementaryInsuranceInformationPremiumRevenue/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember |
| Investment income, net of expenses                                                               | 358us-gaap_SupplementaryInsuranceInformationNetInvestmentIncome/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember                                                                        | 348us-gaap_SupplementaryInsuranceInformationNetInvestmentIncome/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember | 351us-gaap_SupplementaryInsuranceInformationNetInvestmentIncome/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember |
| Benefits, claims losses and settlement expense                                                   | 2,627us-gaap_SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember                                                 | 2,301us-gaap_SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember | 2,137us-gaap_SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember |
| Amortization of deferred policy acquisition costs                                                | 770us-gaap_SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember                                               | 727us-gaap_SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember | 662us-gaap_SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember |
| Underwriting, acquisition and insurance expenses                                                 | 468us-gaap_SupplementaryInsuranceInformationOtherOperatingExpense/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember                                                                      | 456us-gaap_SupplementaryInsuranceInformationOtherOperatingExpense/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember | 414us-gaap_SupplementaryInsuranceInformationOtherOperatingExpense/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember |
| Net written premiums                                                                             | 4,143us-gaap_SupplementaryInsuranceInformationPremiumsWritten/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember                                                                          | 3,893us-gaap_SupplementaryInsuranceInformationPremiumsWritten/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember | 3,482us-gaap_SupplementaryInsuranceInformationPremiumsWritten/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_PropertyLiabilityAndCasualtyInsuranceSegmentMember |
| Accident Health Insurance Segment [Member]                                                       |                                                                                                                                                                                                                                      |   |   |
| **Supplementary Insurance Information, by Segment**                                              |                                                                                                                                                                                                                                      |   |   |
| Net written premiums                                                                             | 3us-gaap_SupplementaryInsuranceInformationPremiumsWritten/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_AccidentAndHealthInsuranceSegmentMember                                                                                         | 2us-gaap_SupplementaryInsuranceInformationPremiumsWritten/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_AccidentAndHealthInsuranceSegmentMember | 3us-gaap_SupplementaryInsuranceInformationPremiumsWritten/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_AccidentAndHealthInsuranceSegmentMember |
| Life Insurance Segment                                                                           |                                                                                                                                                                                                                                      |   |   |
| **Supplementary Insurance Information, by Segment**                                              |                                                                                                                                                                                                                                      |   |   |
| Deferred policy acquisition costs                                                                | 199us-gaap_SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_LifeInsuranceSegmentMember                                                                                     | 199us-gaap_SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_LifeInsuranceSegmentMember | 133us-gaap_SupplementaryInsuranceInformationDeferredPolicyAcquisitionCosts/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_LifeInsuranceSegmentMember |
| Gross future policy benefits, losses, claims and expense losses                                  | 2,519us-gaap_SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_LifeInsuranceSegmentMember                                               | 2,441us-gaap_SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_LifeInsuranceSegmentMember | 2,341us-gaap_SupplementaryInsuranceInformationLiabilityForFuturePolicyBenefitsLossesClaimsAndLossExpenseReserves/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_LifeInsuranceSegmentMember |
| Gross unearned premium                                                                           | 1us-gaap_SupplementaryInsuranceInformationUnearnedPremiums/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_LifeInsuranceSegmentMember                                                                                                     | 2us-gaap_SupplementaryInsuranceInformationUnearnedPremiums/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_LifeInsuranceSegmentMember | 2us-gaap_SupplementaryInsuranceInformationUnearnedPremiums/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_LifeInsuranceSegmentMember |
| Other policy claims and benefits payable                                                         | 25us-gaap_SupplementaryInsuranceInformationOtherPolicyClaimsAndBenefitsPayable/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_LifeInsuranceSegmentMember                                                                                 | 19us-gaap_SupplementaryInsuranceInformationOtherPolicyClaimsAndBenefitsPayable/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_LifeInsuranceSegmentMember | 15us-gaap_SupplementaryInsuranceInformationOtherPolicyClaimsAndBenefitsPayable/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_LifeInsuranceSegmentMember |
| Earned premiums                                                                                  | 198us-gaap_SupplementaryInsuranceInformationPremiumRevenue/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_LifeInsuranceSegmentMember                                                                                                     | 189us-gaap_SupplementaryInsuranceInformationPremiumRevenue/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_LifeInsuranceSegmentMember | 178us-gaap_SupplementaryInsuranceInformationPremiumRevenue/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_LifeInsuranceSegmentMember |
| Investment income, net of expenses                                                               | 144us-gaap_SupplementaryInsuranceInformationNetInvestmentIncome/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_LifeInsuranceSegmentMember                                                                                                | 140us-gaap_SupplementaryInsuranceInformationNetInvestmentIncome/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_LifeInsuranceSegmentMember | 137us-gaap_SupplementaryInsuranceInformationNetInvestmentIncome/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_LifeInsuranceSegmentMember |
| Benefits, claims losses and settlement expense                                                   | 229us-gaap_SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_LifeInsuranceSegmentMember                                                                           | 204us-gaap_SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_LifeInsuranceSegmentMember | 185us-gaap_SupplementaryInsuranceInformationBenefitsClaimsLossesAndSettlementExpense/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_LifeInsuranceSegmentMember |
| Amortization of deferred policy acquisition costs                                                | 37us-gaap_SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_LifeInsuranceSegmentMember                                                                        | 31us-gaap_SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_LifeInsuranceSegmentMember | 45us-gaap_SupplementaryInsuranceInformationAmortizationOfDeferredPolicyAcquisitionCosts/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_LifeInsuranceSegmentMember |
| Underwriting, acquisition and insurance expenses                                                 | $ 26us-gaap_SupplementaryInsuranceInformationOtherOperatingExpense/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_LifeInsuranceSegmentMember                                                                                             | $ 29us-gaap_SupplementaryInsuranceInformationOtherOperatingExpense/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_LifeInsuranceSegmentMember | $ 34us-gaap_SupplementaryInsuranceInformationOtherOperatingExpense/ us-gaap_StatementBusinessSegmentsAxis= us-gaap_LifeInsuranceSegmentMember |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of amortization of deferred policy acquisition costs recognized.
+ References
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| - Definition
Amount of insurance benefits, claims, losses and settlement expenses incurred.
+ References
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| - Definition
Net amount of deferred policy acquisition costs capitalized on contracts remaining in force on the balance sheet date.
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| - Definition
Amount of reserves for future policy claims payable and loss expenses to be incurred.
+ References
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| - Definition
Amount of net investment income earned.
+ References
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| - Definition
Amount of other operating expense incurred.
+ References
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| - Definition
Amount of claims and benefits payable not included within other categories.
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| - Definition
Amount of premium revenue earned.
+ References
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Amount of actual written premiums, including, as applicable, premiums from reinsurance assumed and net of premiums on reinsurance ceded.
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| - Definition
Amount of premiums not yet earned.
+ References
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