| **Condensed Financial Statements Of Parent Company Condensed Balance Sheets (Parenthetical) (Details) (USD $)In Millions, unless otherwise specified** | Dec. 31, 2014                                                                                                                           | Dec. 31, 2013                                                                                                                           |
|--------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------|
| **Condensed Financial Statements, Captions**                                                                                                           |                                                                                                                                    |                                                                                                                                    |
| Land, building and equipment, accumulated depreciation                                                                                                 | $ 446us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment                                                   | $ 420us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment                                                   |
| Cincinnati Financial Corporation                                                                                                                       |                                                                                                                                    |                                                                                                                                    |
| **Condensed Financial Statements, Captions**                                                                                                           |                                                                                                                                    |                                                                                                                                    |
| Land, building and equipment, accumulated depreciation                                                                                                 | $ 112us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment/ dei_LegalEntityAxis= us-gaap_ParentCompanyMember | $ 106us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment/ dei_LegalEntityAxis= us-gaap_ParentCompanyMember |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.14) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 14 -Article 5
+ Details**Name:**us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |
| X                                                                                                                                                                                 |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_CondensedFinancialStatementsCaptionsLineItems**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                       |
|-----------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**dei_LegalEntityAxis=us-gaap_ParentCompanyMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |