| **Summary of Investments Other Than Investments In Related Parties (Details)1 (USD $)In Millions, unless otherwise specified** | Dec. 31, 2014                                                                                                                                                                                                                                                                                                                           | Dec. 31, 2013                                                                                                                                                                                                                                                                                             |
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| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | $ 11,667us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost                                                                                                                                                                                                                                                            |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     |                                                                                                                                                                                                                                                                                                                                    | 0us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue                                                                                                                                                                                                                                |
| Balance sheet                                                                                                                  | 14,386us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Fixed Maturities                                                                                                               |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 8,871us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember                                                                                                                                                                                           |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 9,460us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember                                                                                                                                                                                      |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 9,460us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember                                                                                                                                                                                 |                                                                                                                                                                                                                                                                                                      |
| Equity Securities                                                                                                              |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 2,728us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember                                                                                                                                                                                         |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 4,858us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 4,858us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember                                                                                                                                                                               |                                                                                                                                                                                                                                                                                                      |
| Other than Securities Investment                                                                                               |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 68us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_OtherThanSecuritiesInvestmentMember                                                                                                                                                                               |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     |                                                                                                                                                                                                                                                                                                                                    | 0us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_OtherThanSecuritiesInvestmentMember                                                                                                                                             |
| Balance sheet                                                                                                                  | 68us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_OtherThanSecuritiesInvestmentMember                                                                                                                                                                     |                                                                                                                                                                                                                                                                                                      |
| States, Municipalities and Political Subdivisions | Fixed Maturities                                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 3,267us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USStatesAndPoliticalSubdivisionsMember                                                                                          |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 3,443us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USStatesAndPoliticalSubdivisionsMember                                                                                     |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 3,443us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USStatesAndPoliticalSubdivisionsMember                                                                                |                                                                                                                                                                                                                                                                                                      |
| States, Municipalities and Political Subdivisions | Fixed Maturities | The Cincinnati Insurance Company                        |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 2,634us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USStatesAndPoliticalSubdivisionsMember                              |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 2,759us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USStatesAndPoliticalSubdivisionsMember                         |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 2,759us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USStatesAndPoliticalSubdivisionsMember                    |                                                                                                                                                                                                                                                                                                      |
| States, Municipalities and Political Subdivisions | Fixed Maturities | The Cincinnati Casualty Company                         |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 136us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiCasualtyCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USStatesAndPoliticalSubdivisionsMember                                 |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 143us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiCasualtyCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USStatesAndPoliticalSubdivisionsMember                            |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 143us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiCasualtyCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USStatesAndPoliticalSubdivisionsMember                       |                                                                                                                                                                                                                                                                                                      |
| States, Municipalities and Political Subdivisions | Fixed Maturities | The Cincinnati Indemnity Company                        |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 39us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiIndemnityCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USStatesAndPoliticalSubdivisionsMember                                 |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 41us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiIndemnityCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USStatesAndPoliticalSubdivisionsMember                            |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 41us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiIndemnityCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USStatesAndPoliticalSubdivisionsMember                       |                                                                                                                                                                                                                                                                                                      |
| States, Municipalities and Political Subdivisions | Fixed Maturities | The Cincinnati Life Insurance Company                   |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 187us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiLifeInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USStatesAndPoliticalSubdivisionsMember                            |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 213us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiLifeInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USStatesAndPoliticalSubdivisionsMember                       |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 213us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiLifeInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USStatesAndPoliticalSubdivisionsMember                  |                                                                                                                                                                                                                                                                                                      |
| States, Municipalities and Political Subdivisions | Fixed Maturities | The Cincinnati Specialty Underwriters Insurance Company |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 270us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiSpecialtyUnderwritersInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USStatesAndPoliticalSubdivisionsMember           |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 286us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiSpecialtyUnderwritersInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USStatesAndPoliticalSubdivisionsMember      |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 286us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiSpecialtyUnderwritersInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USStatesAndPoliticalSubdivisionsMember |                                                                                                                                                                                                                                                                                                      |
| States, Municipalities and Political Subdivisions | Fixed Maturities | CSU Producers Resources Inc.                            |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 1us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CSUProducersResourcesIncorporatedMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USStatesAndPoliticalSubdivisionsMember                           |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 1us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CSUProducersResourcesIncorporatedMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USStatesAndPoliticalSubdivisionsMember                      |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 1us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CSUProducersResourcesIncorporatedMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USStatesAndPoliticalSubdivisionsMember                 |                                                                                                                                                                                                                                                                                                      |
| Convertibles and Bonds with Warrants Attached | Fixed Maturities                                                               |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 7us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_ConvertiblesAndBondsWithWarrantsAttachedMember                                                                                      |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 7us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_ConvertiblesAndBondsWithWarrantsAttachedMember                                                                                 |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 7us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_ConvertiblesAndBondsWithWarrantsAttachedMember                                                                            |                                                                                                                                                                                                                                                                                                      |
| Convertibles and Bonds with Warrants Attached | Fixed Maturities | The Cincinnati Insurance Company                            |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 7us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_ConvertiblesAndBondsWithWarrantsAttachedMember                          |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 7us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_ConvertiblesAndBondsWithWarrantsAttachedMember                     |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 7us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_ConvertiblesAndBondsWithWarrantsAttachedMember                |                                                                                                                                                                                                                                                                                                      |
| United States Government | Fixed Maturities                                                                                    |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 7us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USGovernmentAgenciesDebtSecuritiesMember                                                                                            |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 7us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USGovernmentAgenciesDebtSecuritiesMember                                                                                       |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 7us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USGovernmentAgenciesDebtSecuritiesMember                                                                                  |                                                                                                                                                                                                                                                                                                      |
| United States Government | Fixed Maturities | The Cincinnati Insurance Company                                                 |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 1us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USGovernmentAgenciesDebtSecuritiesMember                                |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 1us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USGovernmentAgenciesDebtSecuritiesMember                           |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 1us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USGovernmentAgenciesDebtSecuritiesMember                      |                                                                                                                                                                                                                                                                                                      |
| United States Government | Fixed Maturities | The Cincinnati Casualty Company                                                  |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 2us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiCasualtyCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USGovernmentAgenciesDebtSecuritiesMember                                 |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 2us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiCasualtyCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USGovernmentAgenciesDebtSecuritiesMember                            |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 2us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiCasualtyCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USGovernmentAgenciesDebtSecuritiesMember                       |                                                                                                                                                                                                                                                                                                      |
| United States Government | Fixed Maturities | The Cincinnati Indemnity Company                                                 |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 1us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiIndemnityCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USGovernmentAgenciesDebtSecuritiesMember                                |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 1us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiIndemnityCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USGovernmentAgenciesDebtSecuritiesMember                           |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 1us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiIndemnityCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USGovernmentAgenciesDebtSecuritiesMember                      |                                                                                                                                                                                                                                                                                                      |
| United States Government | Fixed Maturities | The Cincinnati Life Insurance Company                                            |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 3us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiLifeInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USGovernmentAgenciesDebtSecuritiesMember                            |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 3us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiLifeInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USGovernmentAgenciesDebtSecuritiesMember                       |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 3us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiLifeInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USGovernmentAgenciesDebtSecuritiesMember                  |                                                                                                                                                                                                                                                                                                      |
| Government-Sponsored Enterprises | Fixed Maturities                                                                            |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 213us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember                                                                              |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 208us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember                                                                         |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 208us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember                                                                    |                                                                                                                                                                                                                                                                                                      |
| Government-Sponsored Enterprises | Fixed Maturities | The Cincinnati Insurance Company                                         |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 4us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember                    |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 4us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember               |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 4us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember          |                                                                                                                                                                                                                                                                                                      |
| Government-Sponsored Enterprises | Fixed Maturities | The Cincinnati Life Insurance Company                                    |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 209us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiLifeInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember              |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 204us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiLifeInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember         |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 204us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiLifeInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember    |                                                                                                                                                                                                                                                                                                      |
| Foreign Government | Fixed Maturities                                                                                          |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 10us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= cinf_ForeignGovernmentMember                                                                                                               |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 10us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= cinf_ForeignGovernmentMember                                                                                                          |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 10us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= cinf_ForeignGovernmentMember                                                                                                     |                                                                                                                                                                                                                                                                                                      |
| Foreign Government | Fixed Maturities | The Cincinnati Insurance Company                                                       |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 10us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= cinf_ForeignGovernmentMember                                                   |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 10us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= cinf_ForeignGovernmentMember                                              |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 10us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= cinf_ForeignGovernmentMember                                         |                                                                                                                                                                                                                                                                                                      |
| Common Stock | Equity Securities                                                                                               |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 2,583us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_CommonStockMember                                                                                                             |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 4,679us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_CommonStockMember                                                                                                        |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 4,679us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_CommonStockMember                                                                                                   |                                                                                                                                                                                                                                                                                                      |
| Common Stock | Equity Securities | The Cincinnati Insurance Company                                                            |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 1,462us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_CommonStockMember                                                 |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 2,831us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_CommonStockMember                                            |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 2,831us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_CommonStockMember                                       |                                                                                                                                                                                                                                                                                                      |
| Common Stock | Equity Securities | The Cincinnati Casualty Company                                                             |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 45us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiCasualtyCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_CommonStockMember                                                     |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 91us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiCasualtyCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_CommonStockMember                                                |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 91us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiCasualtyCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_CommonStockMember                                           |                                                                                                                                                                                                                                                                                                      |
| Common Stock | Equity Securities | The Cincinnati Indemnity Company                                                            |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 12us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiIndemnityCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_CommonStockMember                                                    |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 22us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiIndemnityCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_CommonStockMember                                               |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 22us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiIndemnityCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_CommonStockMember                                          |                                                                                                                                                                                                                                                                                                      |
| Common Stock | Equity Securities | The Cincinnati Specialty Underwriters Insurance Company                                     |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 51us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiSpecialtyUnderwritersInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_CommonStockMember                               |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 85us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiSpecialtyUnderwritersInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_CommonStockMember                          |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 85us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiSpecialtyUnderwritersInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_CommonStockMember                     |                                                                                                                                                                                                                                                                                                      |
| Common Stock | Equity Securities | CSU Producers Resources Inc.                                                                |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 9us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember/ dei_LegalEntityAxis= cinf_CSUProducersResourcesIncorporatedMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_CommonStockMember                                              |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 11us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember/ dei_LegalEntityAxis= cinf_CSUProducersResourcesIncorporatedMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_CommonStockMember                                        |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 11us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember/ dei_LegalEntityAxis= cinf_CSUProducersResourcesIncorporatedMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_CommonStockMember                                   |                                                                                                                                                                                                                                                                                                      |
| Common Stock | Equity Securities | Cincinnati Financial Corporation                                                            |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 1,004us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember/ dei_LegalEntityAxis= us-gaap_ParentCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_CommonStockMember                                                           |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 1,639us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember/ dei_LegalEntityAxis= us-gaap_ParentCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_CommonStockMember                                                      |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 1,639us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember/ dei_LegalEntityAxis= us-gaap_ParentCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_CommonStockMember                                                 |                                                                                                                                                                                                                                                                                                      |
| Nonredeemable Preferred Stock | Equity Securities                                                                              |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 145us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_NonredeemablePreferredStockMember                                                                                               |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 179us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_NonredeemablePreferredStockMember                                                                                          |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 179us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_NonredeemablePreferredStockMember                                                                                     |                                                                                                                                                                                                                                                                                                      |
| Nonredeemable Preferred Stock | Equity Securities | The Cincinnati Insurance Company                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 137us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_NonredeemablePreferredStockMember                                   |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 167us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_NonredeemablePreferredStockMember                              |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 167us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_NonredeemablePreferredStockMember                         |                                                                                                                                                                                                                                                                                                      |
| Nonredeemable Preferred Stock | Equity Securities | The Cincinnati Life Insurance Company                                      |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 5us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiLifeInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_NonredeemablePreferredStockMember                                 |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 8us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiLifeInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_NonredeemablePreferredStockMember                            |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 8us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiLifeInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_NonredeemablePreferredStockMember                       |                                                                                                                                                                                                                                                                                                      |
| Nonredeemable Preferred Stock | Equity Securities | Cincinnati Financial Corporation                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 3us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember/ dei_LegalEntityAxis= us-gaap_ParentCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_NonredeemablePreferredStockMember                                               |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 4us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember/ dei_LegalEntityAxis= us-gaap_ParentCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_NonredeemablePreferredStockMember                                          |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 4us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_EquitySecuritiesMember/ dei_LegalEntityAxis= us-gaap_ParentCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_NonredeemablePreferredStockMember                                     |                                                                                                                                                                                                                                                                                                      |
| All Other Corporate Bonds | Fixed Maturities                                                                                   |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 5,367us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_AllOtherCorporateBondsMember                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 5,785us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_AllOtherCorporateBondsMember                                                                                               |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 5,785us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_AllOtherCorporateBondsMember                                                                                          |                                                                                                                                                                                                                                                                                                      |
| All Other Corporate Bonds | Fixed Maturities | The Cincinnati Insurance Company                                                |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 2,507us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_AllOtherCorporateBondsMember                                        |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 2,706us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_AllOtherCorporateBondsMember                                   |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 2,706us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_AllOtherCorporateBondsMember                              |                                                                                                                                                                                                                                                                                                      |
| All Other Corporate Bonds | Fixed Maturities | The Cincinnati Casualty Company                                                 |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 110us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiCasualtyCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_AllOtherCorporateBondsMember                                           |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 118us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiCasualtyCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_AllOtherCorporateBondsMember                                      |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 118us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiCasualtyCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_AllOtherCorporateBondsMember                                 |                                                                                                                                                                                                                                                                                                      |
| All Other Corporate Bonds | Fixed Maturities | The Cincinnati Indemnity Company                                                |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 21us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiIndemnityCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_AllOtherCorporateBondsMember                                           |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 23us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiIndemnityCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_AllOtherCorporateBondsMember                                      |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 23us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiIndemnityCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_AllOtherCorporateBondsMember                                 |                                                                                                                                                                                                                                                                                                      |
| All Other Corporate Bonds | Fixed Maturities | The Cincinnati Life Insurance Company                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 2,517us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiLifeInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_AllOtherCorporateBondsMember                                    |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 2,706us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiLifeInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_AllOtherCorporateBondsMember                               |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 2,706us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiLifeInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_AllOtherCorporateBondsMember                          |                                                                                                                                                                                                                                                                                                      |
| All Other Corporate Bonds | Fixed Maturities | The Cincinnati Specialty Underwriters Insurance Company                         |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 151us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiSpecialtyUnderwritersInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_AllOtherCorporateBondsMember                     |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 159us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiSpecialtyUnderwritersInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_AllOtherCorporateBondsMember                |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 159us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CincinnatiSpecialtyUnderwritersInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_AllOtherCorporateBondsMember           |                                                                                                                                                                                                                                                                                                      |
| All Other Corporate Bonds | Fixed Maturities | CSU Producers Resources Inc.                                                    |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 4us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CSUProducersResourcesIncorporatedMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_AllOtherCorporateBondsMember                                     |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 4us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CSUProducersResourcesIncorporatedMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_AllOtherCorporateBondsMember                                |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 4us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= cinf_CSUProducersResourcesIncorporatedMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_AllOtherCorporateBondsMember                           |                                                                                                                                                                                                                                                                                                      |
| All Other Corporate Bonds | Fixed Maturities | Cincinnati Financial Corporation                                                |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 57us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= us-gaap_ParentCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_AllOtherCorporateBondsMember                                                     |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     | 69us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= us-gaap_ParentCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_AllOtherCorporateBondsMember                                                |                                                                                                                                                                                                                                                                                                      |
| Balance sheet                                                                                                                  | 69us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_DebtSecuritiesMember/ dei_LegalEntityAxis= us-gaap_ParentCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_AllOtherCorporateBondsMember                                           |                                                                                                                                                                                                                                                                                                      |
| Policy Loans | Other than Securities Investment | The Cincinnati Life Insurance Company                                        |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 31us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_OtherThanSecuritiesInvestmentMember/ dei_LegalEntityAxis= cinf_CincinnatiLifeInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_PolicyLoansMember                                   |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     |                                                                                                                                                                                                                                                                                                                                    | 0us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_OtherThanSecuritiesInvestmentMember/ dei_LegalEntityAxis= cinf_CincinnatiLifeInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_PolicyLoansMember |
| Balance sheet                                                                                                                  | 31us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_OtherThanSecuritiesInvestmentMember/ dei_LegalEntityAxis= cinf_CincinnatiLifeInsuranceCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= us-gaap_PolicyLoansMember                         |                                                                                                                                                                                                                                                                                                      |
| Limited Partnership | Other than Securities Investment | Cincinnati Financial Corporation                                      |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| **Summary Of Investments Other Than Investments In Related Parties Reportable Data**                                           |                                                                                                                                                                                                                                                                                                                                    |                                                                                                                                                                                                                                                                                                      |
| Cost or amortized cost                                                                                                         | 37us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost/ invest_InvestmentSecuritiesClassAxis= us-gaap_OtherThanSecuritiesInvestmentMember/ dei_LegalEntityAxis= us-gaap_ParentCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= cinf_LimitedPartnershipMember                                             |                                                                                                                                                                                                                                                                                                      |
| Fair value                                                                                                                     |                                                                                                                                                                                                                                                                                                                                    | 0us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue/ invest_InvestmentSecuritiesClassAxis= us-gaap_OtherThanSecuritiesInvestmentMember/ dei_LegalEntityAxis= us-gaap_ParentCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= cinf_LimitedPartnershipMember           |
| Balance sheet                                                                                                                  | $ 37us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount/ invest_InvestmentSecuritiesClassAxis= us-gaap_OtherThanSecuritiesInvestmentMember/ dei_LegalEntityAxis= us-gaap_ParentCompanyMember/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis= cinf_LimitedPartnershipMember                                 |                                                                                                                                                                                                                                                                                                      |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
This element represents the carrying (reported) amount of the entity's investments as of the balance sheet date. This amount may represent the individual investment's or group of similar investments' original cost, fair value, or such other amount at which the investment is shown in the entity's balance sheet.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 15 -Article 12Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 320 -Section S99 -Paragraph 7 -Subparagraph (SX 210.12-15) -URI http://asc.fasb.org/extlink&oid=34726532&loc=d3e611379-123010
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
This item represents the original cost of the entity's investments including investments in equity securities and, as to fixed maturities, original cost reduced by repayments and adjusted for amortization of premiums or accrual of discounts.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 15 -Article 12Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 320 -Section S99 -Paragraph 7 -Subparagraph (SX 210.12-15) -URI http://asc.fasb.org/extlink&oid=34726532&loc=d3e611379-123010
+ Details**Name:**us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
This item represents the reported amount of the entity's investments measured at fair value. Fair value is the price that would be received to sell an investment in an orderly transaction between market participants at the balance sheet [measurement] date.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 15 -Article 12Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 320 -Section S99 -Paragraph 7 -Subparagraph (SX 210.12-15) -URI http://asc.fasb.org/extlink&oid=34726532&loc=d3e611379-123010
+ Details**Name:**us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
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| - Details**Name:**us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesReportableDataLineItems**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
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| - Details**Name:**us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=cinf_ForeignGovernmentMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
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|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=cinf_LimitedPartnershipMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
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| - Details**Name:**us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_AllOtherCorporateBondsMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
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| - Details**Name:**us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_CommonStockMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
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| - Details**Name:**us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_NonredeemablePreferredStockMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
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| - Details**Name:**us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_PolicyLoansMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
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| - Details**Name:**us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_USGovernmentAgenciesDebtSecuritiesMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
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