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The element may be used in both the balance sheet and disclosure in the same submission.No definition available.false2Fair value of senior debt39false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse21false USDtruefalse$I2013Q2_us-gaap_DebtInstrumentAxis_cinf_SeniorDebentures692PercentDue2028Member_us-gaap_FairValueByFairValueHierarchyLevelAxis_us-gaap_FairValueInputsLevel2Memberhttp://www.sec.gov/CIK0000020286instant2013-06-30T00:00:000001-01-01T00:00:00falsefalseSignificant other observable inputs (Level 2)us-gaap_FairValueByFairValueHierarchyLevelAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_FairValueInputsLevel2Memberus-gaap_FairValueByFairValueHierarchyLevelAxisexplicitMemberfalsefalseSenior Debentures 6.920 % Due 2028us-gaap_DebtInstrumentAxisxbrldihttp://xbrl.org/2006/xbrldicinf_SeniorDebentures692PercentDue2028Memberus-gaap_DebtInstrumentAxisexplicitMemberusdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0Significant other observable inputs (Level 2) | Senior Debentures 6.920 % Due 202840true 3us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]41false 4us-gaap_LongTermDebtFairValueus-gaap_truecreditinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse469000000469USD$falsefalsefalse2truefalsefalse479000000479USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.No definition available.false2Fair value of senior debt42false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse23false USDtruefalse$I2013Q2_us-gaap_DebtInstrumentAxis_cinf_SeniorNotes6125PercentDue2034Member_us-gaap_FairValueByFairValueHierarchyLevelAxis_us-gaap_FairValueInputsLevel2Memberhttp://www.sec.gov/CIK0000020286instant2013-06-30T00:00:000001-01-01T00:00:00falsefalseSignificant other observable inputs (Level 2)us-gaap_FairValueByFairValueHierarchyLevelAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_FairValueInputsLevel2Memberus-gaap_FairValueByFairValueHierarchyLevelAxisexplicitMemberfalsefalseSenior Notes 6.125 % Due 2034us-gaap_DebtInstrumentAxisxbrldihttp://xbrl.org/2006/xbrldicinf_SeniorNotes6125PercentDue2034Memberus-gaap_DebtInstrumentAxisexplicitMemberusdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0Significant other observable inputs (Level 2) | Senior Notes 6.125 % Due 203443true 3us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]44false 4us-gaap_LongTermDebtFairValueus-gaap_truecreditinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse402000000402USD$falsefalsefalse2truefalsefalse431000000431USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.No definition available.false2Fair value of senior debt45false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse25false USDtruefalse$I2013Q2_us-gaap_FairValueByFairValueHierarchyLevelAxis_us-gaap_FairValueInputsLevel3Memberhttp://www.sec.gov/CIK0000020286instant2013-06-30T00:00:000001-01-01T00:00:00falsefalseSignificant unobservable inputs (Level 3)us-gaap_FairValueByFairValueHierarchyLevelAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_FairValueInputsLevel3Memberus-gaap_FairValueByFairValueHierarchyLevelAxisexplicitMemberusdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0Significant unobservable inputs (Level 3)46true 3us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]47false 4us-gaap_NotesPayableFairValueDisclosureus-gaap_truecreditinstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse00USD$falsefalsefalse2truefalsefalse00USD$falsefalsefalsexbrli:monetaryItemTypemonetaryFair value portion of notes payable.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19, 20, 22 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19,20,22) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 false2Fair value of note payable48false 4us-gaap_DebtInstrumentFairValueus-gaap_truecreditinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse00USD$falsefalsefalse2truefalsefalse00USD$falsefalsefalsexbrli:monetaryItemTypemonetaryFair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=28364263&loc=d3e13433-108611 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=28364263&loc=d3e13476-108611 false2Total49false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse27false USDtruefalse$I2013Q2_us-gaap_DebtInstrumentAxis_cinf_SeniorDebentures69PercentDue2028Member_us-gaap_FairValueByFairValueHierarchyLevelAxis_us-gaap_FairValueInputsLevel3Memberhttp://www.sec.gov/CIK0000020286instant2013-06-30T00:00:000001-01-01T00:00:00falsefalseSignificant unobservable inputs (Level 3)us-gaap_FairValueByFairValueHierarchyLevelAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_FairValueInputsLevel3Memberus-gaap_FairValueByFairValueHierarchyLevelAxisexplicitMemberfalsefalseSenior Debentures 6.900 % Due 2028us-gaap_DebtInstrumentAxisxbrldihttp://xbrl.org/2006/xbrldicinf_SeniorDebentures69PercentDue2028Memberus-gaap_DebtInstrumentAxisexplicitMemberusdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0Significant unobservable inputs (Level 3) | Senior Debentures 6.900 % Due 202850true 3us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]51false 4us-gaap_LongTermDebtFairValueus-gaap_truecreditinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse00USD$falsefalsefalse2truefalsefalse00USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.No definition available.false2Fair value of senior debt52false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse29false USDtruefalse$I2013Q2_us-gaap_DebtInstrumentAxis_cinf_SeniorDebentures692PercentDue2028Member_us-gaap_FairValueByFairValueHierarchyLevelAxis_us-gaap_FairValueInputsLevel3Memberhttp://www.sec.gov/CIK0000020286instant2013-06-30T00:00:000001-01-01T00:00:00falsefalseSignificant unobservable inputs (Level 3)us-gaap_FairValueByFairValueHierarchyLevelAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_FairValueInputsLevel3Memberus-gaap_FairValueByFairValueHierarchyLevelAxisexplicitMemberfalsefalseSenior Debentures 6.920 % Due 2028us-gaap_DebtInstrumentAxisxbrldihttp://xbrl.org/2006/xbrldicinf_SeniorDebentures692PercentDue2028Memberus-gaap_DebtInstrumentAxisexplicitMemberusdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0Significant unobservable inputs (Level 3) | Senior Debentures 6.920 % Due 202853true 3us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]54false 4us-gaap_LongTermDebtFairValueus-gaap_truecreditinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse00USD$falsefalsefalse2truefalsefalse00USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.No definition available.false2Fair value of senior debt55false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse31false USDtruefalse$I2013Q2_us-gaap_DebtInstrumentAxis_cinf_SeniorNotes6125PercentDue2034Member_us-gaap_FairValueByFairValueHierarchyLevelAxis_us-gaap_FairValueInputsLevel3Memberhttp://www.sec.gov/CIK0000020286instant2013-06-30T00:00:000001-01-01T00:00:00falsefalseSignificant unobservable inputs (Level 3)us-gaap_FairValueByFairValueHierarchyLevelAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_FairValueInputsLevel3Memberus-gaap_FairValueByFairValueHierarchyLevelAxisexplicitMemberfalsefalseSenior Notes 6.125 % Due 2034us-gaap_DebtInstrumentAxisxbrldihttp://xbrl.org/2006/xbrldicinf_SeniorNotes6125PercentDue2034Memberus-gaap_DebtInstrumentAxisexplicitMemberusdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0Significant unobservable inputs (Level 3) | Senior Notes 6.125 % Due 203456true 3us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]57false 4us-gaap_LongTermDebtFairValueus-gaap_truecreditinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse00USD$falsetruefalse2truefalsefalse00USD$falsetruefalsexbrli:monetaryItemTypemonetaryThe fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.No definition available.false2Fair value of senior debtfalseFair Value Measurements - Fair Values of Note Payable and Long-Term Debt (Detail) (USD $)MillionsUnKnownUnKnownUnKnowntruefalsefalseSheethttp://www.cinfin.com/role/FairValueMeasurementsFairValuesOfNotePayableAndLongTermDebtDetail257