<?xml version="1.0" encoding="utf-8"?>
<FilingSummary xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <Version>2.4.0.6</Version>
  <ProcessingTime />
  <ReportFormat>Html</ReportFormat>
  <ContextCount>336</ContextCount>
  <ElementCount>295</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>77</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>6</UnitCount>
  <MyReports>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0001000 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/DocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
    </Report>
    <Report>
      <IsDefault>true</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>1001000 - Statement - Condensed Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/CondensedConsolidatedBalanceSheets</Role>
      <ShortName>Condensed Consolidated Balance Sheets</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>1001501 - Statement - Condensed Consolidated Balance Sheets (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/CondensedConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>Condensed Consolidated Balance Sheets (Parenthetical)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>1002000 - Statement - Condensed Consolidated Statements of Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/CondensedConsolidatedStatementsOfIncome</Role>
      <ShortName>Condensed Consolidated Statements of Income</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>1003000 - Statement - Condensed Consolidated Statements of Comprehensive Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/CondensedConsolidatedStatementsOfComprehensiveIncome</Role>
      <ShortName>Condensed Consolidated Statements of Comprehensive Income</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>1003001 - Statement - Condensed Consolidated Statements of Comprehensive Income (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeParenthetical</Role>
      <ShortName>Condensed Consolidated Statements of Comprehensive Income (Parenthetical)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>1004000 - Statement - Condensed Consolidated Statements of Shareholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/CondensedConsolidatedStatementsOfShareholdersEquity</Role>
      <ShortName>Condensed Consolidated Statements of Shareholders' Equity</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>1005000 - Statement - Condensed Consolidated Statements of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/CondensedConsolidatedStatementsOfCashFlows</Role>
      <ShortName>Condensed Consolidated Statements of Cash Flows</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>2101100 - Disclosure - Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/AccountingPolicies</Role>
      <ShortName>Accounting Policies</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>2102100 - Disclosure - Investments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/Investments</Role>
      <ShortName>Investments</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>2103100 - Disclosure - Fair Value Measurements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/FairValueMeasurements</Role>
      <ShortName>Fair Value Measurements</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>2104100 - Disclosure - Property Casualty Loss and Loss Expenses</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/PropertyCasualtyLossAndLossExpenses</Role>
      <ShortName>Property Casualty Loss and Loss Expenses</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>2105100 - Disclosure - Life Policy and Investment Contract Reserves</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/LifePolicyAndInvestmentContractReserves</Role>
      <ShortName>Life Policy and Investment Contract Reserves</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>2106100 - Disclosure - Deferred Acquisition Costs</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/DeferredAcquisitionCosts</Role>
      <ShortName>Deferred Acquisition Costs</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>2107100 - Disclosure - Accumulated Other Comprehensive Income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/AccumulatedOtherComprehensiveIncome</Role>
      <ShortName>Accumulated Other Comprehensive Income</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>2108100 - Disclosure - Reinsurance</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/Reinsurance</Role>
      <ShortName>Reinsurance</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>2109100 - Disclosure - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/IncomeTaxes</Role>
      <ShortName>Income Taxes</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>2110100 - Disclosure - Net Income Per Common Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/NetIncomePerCommonShare</Role>
      <ShortName>Net Income Per Common Share</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>2111100 - Disclosure - Employee Retirement Benefits</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/EmployeeRetirementBenefits</Role>
      <ShortName>Employee Retirement Benefits</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>2112100 - Disclosure - Commitments and Contingent Liabilities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/CommitmentsAndContingentLiabilities</Role>
      <ShortName>Commitments and Contingent Liabilities</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>2113100 - Disclosure - Segment Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/SegmentInformation</Role>
      <ShortName>Segment Information</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>2201201 - Disclosure - Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/AccountingPoliciesPolicies</Role>
      <ShortName>Accounting Policies (Policies)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>2302301 - Disclosure - Investments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/InvestmentsTables</Role>
      <ShortName>Investments (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>2303301 - Disclosure - Fair Value Measurements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/FairValueMeasurementsTables</Role>
      <ShortName>Fair Value Measurements (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>2304301 - Disclosure - Property Casualty Loss and Loss Expenses (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/PropertyCasualtyLossAndLossExpensesTables</Role>
      <ShortName>Property Casualty Loss and Loss Expenses (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>2305301 - Disclosure - Life Policy and Investment Contract Reserves (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/LifePolicyAndInvestmentContractReservesTables</Role>
      <ShortName>Life Policy and Investment Contract Reserves (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>2306301 - Disclosure - Deferred Acquisition Costs  (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/DeferredAcquisitionCostsTables</Role>
      <ShortName>Deferred Acquisition Costs  (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>2307301 - Disclosure - Accumulated Other Comprehensive Income (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/AccumulatedOtherComprehensiveIncomeTables</Role>
      <ShortName>Accumulated Other Comprehensive Income (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>2308301 - Disclosure - Reinsurance (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/ReinsuranceTables</Role>
      <ShortName>Reinsurance (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>2309301 - Disclosure - Income Taxes (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/IncomeTaxesTables</Role>
      <ShortName>Income Taxes (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>2310301 - Disclosure - Net Income Per Common Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/NetIncomePerCommonShareTables</Role>
      <ShortName>Net Income Per Common Share (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>2311301 - Disclosure - Employee Retirement Benefits (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/EmployeeRetirementBenefitsTables</Role>
      <ShortName>Employee Retirement Benefits (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>2313301 - Disclosure - Segment Information (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/SegmentInformationTables</Role>
      <ShortName>Segment Information (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>2402402 - Disclosure - Investments - Analysis of Cost or Amortized Cost, Gross Unrealized Gains and Losses and Fair Value for Investments (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/InvestmentsAnalysisOfCostOrAmortizedCostGrossUnrealizedGainsAndLossesAndFairValueForInvestmentsDetail</Role>
      <ShortName>Investments - Analysis of Cost or Amortized Cost, Gross Unrealized Gains and Losses and Fair Value for Investments (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>2402403 - Disclosure - Investments - Fair Values and Unrealized Losses by Investment Category and by Duration of Securities' Continuous Unrealized Loss Position (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/InvestmentsFairValuesAndUnrealizedLossesByInvestmentCategoryAndByDurationOfSecuritiesContinuousUnrealizedLossPositionDetail</Role>
      <ShortName>Investments - Fair Values and Unrealized Losses by Investment Category and by Duration of Securities' Continuous Unrealized Loss Position (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>2402404 - Disclosure - Investments - Realized Investment Gains and Losses and Change in Unrealized Investment Gains and Losses and Other Items (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/InvestmentsRealizedInvestmentGainsAndLossesAndChangeInUnrealizedInvestmentGainsAndLossesAndOtherItemsDetail</Role>
      <ShortName>Investments - Realized Investment Gains and Losses and Change in Unrealized Investment Gains and Losses and Other Items (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>2402405 - Disclosure - Investments - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/InvestmentsAdditionalInformationDetail</Role>
      <ShortName>Investments - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>2403402 - Disclosure - Fair Value Measurements - Fair Value Hierarchy for Assets Measured at Fair Value on Recurring Basis (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/FairValueMeasurementsFairValueHierarchyForAssetsMeasuredAtFairValueOnRecurringBasisDetail</Role>
      <ShortName>Fair Value Measurements - Fair Value Hierarchy for Assets Measured at Fair Value on Recurring Basis (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>2403403 - Disclosure - Fair Value Measurements - Change in Level 3 Assets (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/FairValueMeasurementsChangeInLevel3AssetsDetail</Role>
      <ShortName>Fair Value Measurements - Change in Level 3 Assets (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>2403404 - Disclosure - Fair Value Measurements - Summary of Book Value and Principal Amounts of Long-Term Debt (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/FairValueMeasurementsSummaryOfBookValueAndPrincipalAmountsOfLongTermDebtDetail</Role>
      <ShortName>Fair Value Measurements - Summary of Book Value and Principal Amounts of Long-Term Debt (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>2403405 - Disclosure - Fair Value Measurements - Fair Values of Note Payable and Long-Term Debt (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/FairValueMeasurementsFairValuesOfNotePayableAndLongTermDebtDetail</Role>
      <ShortName>Fair Value Measurements - Fair Values of Note Payable and Long-Term Debt (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>2403406 - Disclosure - Fair Value Measurements - Fair Value of Life Policy Loans (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/FairValueMeasurementsFairValueOfLifePolicyLoansDetail</Role>
      <ShortName>Fair Value Measurements - Fair Value of Life Policy Loans (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>2403407 - Disclosure - Fair Value Measurements - Fair Values of Deferred Annuities, Structured Settlements and Other Items (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/FairValueMeasurementsFairValuesOfDeferredAnnuitiesStructuredSettlementsAndOtherItemsDetail</Role>
      <ShortName>Fair Value Measurements - Fair Values of Deferred Annuities, Structured Settlements and Other Items (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>2403408 - Disclosure - Fair Value Measurements - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/FairValueMeasurementsAdditionalInformationDetail</Role>
      <ShortName>Fair Value Measurements - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>2404402 - Disclosure - Property Casualty Loss and Loss Expenses - Consolidated Property Casualty Loss and Loss Expense Reserves (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/PropertyCasualtyLossAndLossExpensesConsolidatedPropertyCasualtyLossAndLossExpenseReservesDetail</Role>
      <ShortName>Property Casualty Loss and Loss Expenses - Consolidated Property Casualty Loss and Loss Expense Reserves (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>2404403 - Disclosure - Property Casualty Loss and Loss Expenses  - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/PropertyCasualtyLossAndLossExpensesAdditionalInformationDetail</Role>
      <ShortName>Property Casualty Loss and Loss Expenses  - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>2405402 - Disclosure - Reserves in Addition to Account Balance, Based on Expected No-Lapse Guarantee Benefits and Expected Policy Assessments (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/ReservesInAdditionToAccountBalanceBasedOnExpectedNoLapseGuaranteeBenefitsAndExpectedPolicyAssessmentsDetail</Role>
      <ShortName>Reserves in Addition to Account Balance, Based on Expected No-Lapse Guarantee Benefits and Expected Policy Assessments (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>2406402 - Disclosure - Deferred Acquisition Costs - Deferred Policy Acquisition Costs and Asset Reconciliation (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/DeferredAcquisitionCostsDeferredPolicyAcquisitionCostsAndAssetReconciliationDetail</Role>
      <ShortName>Deferred Acquisition Costs - Deferred Policy Acquisition Costs and Asset Reconciliation (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>2407402 - Disclosure - Accumulated Other Comprehensive Income (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/AccumulatedOtherComprehensiveIncomeDetails</Role>
      <ShortName>Accumulated Other Comprehensive Income (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>2408402 - Disclosure - Reinsurance - Earned Consolidated Property Casualty Insurance Premiums on Assumed and Ceded Business (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/ReinsuranceEarnedConsolidatedPropertyCasualtyInsurancePremiumsOnAssumedAndCededBusinessDetail</Role>
      <ShortName>Reinsurance - Earned Consolidated Property Casualty Insurance Premiums on Assumed and Ceded Business (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>2408403 - Disclosure - Reinsurance - Incurred Consolidated Property Casualty Insurance Loss and Loss Expenses on Assumed and Ceded Business (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/ReinsuranceIncurredConsolidatedPropertyCasualtyInsuranceLossAndLossExpensesOnAssumedAndCededBusinessDetail</Role>
      <ShortName>Reinsurance - Incurred Consolidated Property Casualty Insurance Loss and Loss Expenses on Assumed and Ceded Business (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>2408404 - Disclosure - Reinsurance - Earned Life Insurance Premiums on Ceded Business (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/ReinsuranceEarnedLifeInsurancePremiumsOnCededBusinessDetail</Role>
      <ShortName>Reinsurance - Earned Life Insurance Premiums on Ceded Business (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>2408405 - Disclosure - Reinsurance - Life Insurance Contract Holders' Benefits Incurred on Ceded Business (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/ReinsuranceLifeInsuranceContractHoldersBenefitsIncurredOnCededBusinessDetail</Role>
      <ShortName>Reinsurance - Life Insurance Contract Holders' Benefits Incurred on Ceded Business (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>2409402 - Disclosure - Income Taxes - Differences Between 35 Percent Statutory Income Tax Rate and Effective Income Tax Rate (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/IncomeTaxesDifferencesBetween35PercentStatutoryIncomeTaxRateAndEffectiveIncomeTaxRateDetail</Role>
      <ShortName>Income Taxes - Differences Between 35 Percent Statutory Income Tax Rate and Effective Income Tax Rate (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>2409403 - Disclosure - Income Taxes (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/IncomeTaxesNarrativeDetails</Role>
      <ShortName>Income Taxes (Narrative) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>2410402 - Disclosure - Net Income Per Common Share - Calculations for Basic and Diluted Earnings Per Share (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/NetIncomePerCommonShareCalculationsForBasicAndDilutedEarningsPerShareDetail</Role>
      <ShortName>Net Income Per Common Share - Calculations for Basic and Diluted Earnings Per Share (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>2411402 - Disclosure - Employee Retirement Benefits - Components of Net Periodic Costs for Qualified and Supplemental Pension Plans (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/EmployeeRetirementBenefitsComponentsOfNetPeriodicCostsForQualifiedAndSupplementalPensionPlansDetail</Role>
      <ShortName>Employee Retirement Benefits - Components of Net Periodic Costs for Qualified and Supplemental Pension Plans (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>2411403 - Disclosure - Employee Retirement Benefits - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/EmployeeRetirementBenefitsAdditionalInformationDetail</Role>
      <ShortName>Employee Retirement Benefits - Additional Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>2412401 - Disclosure - Commitments and Contingent Liabilities (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/CommitmentsAndContingentLiabilitiesNarrativeDetails</Role>
      <ShortName>Commitments and Contingent Liabilities (Narrative) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>2413402 - Disclosure - Segment Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/SegmentInformationDetail</Role>
      <ShortName>Segment Information (Detail)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>2413403 - Disclosure - Segment Information - Narrative (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.cinfin.com/role/SegmentInformationNarrativeDetails</Role>
      <ShortName>Segment Information - Narrative (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <Logs>
    <Log type="Info">Process Flow-Through: 1001000 - Statement - Condensed Consolidated Balance Sheets</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Mar. 31, 2012'</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Dec. 31, 2011'</Log>
    <Log type="Info">Process Flow-Through: 1001501 - Statement - Condensed Consolidated Balance Sheets (Parenthetical)</Log>
    <Log type="Info">Process Flow-Through: 1002000 - Statement - Condensed Consolidated Statements of Income</Log>
    <Log type="Info">Process Flow-Through: 1003000 - Statement - Condensed Consolidated Statements of Comprehensive Income</Log>
    <Log type="Info">Process Flow-Through: 1003001 - Statement - Condensed Consolidated Statements of Comprehensive Income (Parenthetical)</Log>
    <Log type="Info">Process Flow-Through: 1005000 - Statement - Condensed Consolidated Statements of Cash Flows</Log>
  </Logs>
  <InputFiles>
    <File>cinf-20130331.xml</File>
    <File>cinf-20130331.xsd</File>
    <File>cinf-20130331_cal.xml</File>
    <File>cinf-20130331_def.xml</File>
    <File>cinf-20130331_lab.xml</File>
    <File>cinf-20130331_pre.xml</File>
  </InputFiles>
  <SupplementalFiles />
  <BaseTaxonomies />
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
