| **Employee Retirement Benefits (Weighted-Average Assumptions Used) (Details)** | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                           |
|--------------------------------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
||
| Benefit Obligations | Pension Plan                                             |                                                                                                                                                                                                                                                                                                                                                                      |   |   |
| **Schedule of Benefit Obligations Weighted Average Assumptions**               |                                                                                                                                                                                                                                                                                                                                                                      |   |   |
| Discount rate                                                                  | 4.25%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate/ cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis= cinf_BenefitObligationsMember/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember                                                                                   | 5.15%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate/ cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis= cinf_BenefitObligationsMember/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember |   |
| Benefit Obligations | Pension Plan | Minimum                                   |                                                                                                                                                                                                                                                                                                                                                                      |   |   |
| **Schedule of Benefit Obligations Weighted Average Assumptions**               |                                                                                                                                                                                                                                                                                                                                                                      |   |   |
| Rate of compensation increase                                                  | 2.75%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease/ cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis= cinf_BenefitObligationsMember/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember/ us-gaap_RangeAxis= us-gaap_MinimumMember                           | 2.75%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease/ cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis= cinf_BenefitObligationsMember/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember/ us-gaap_RangeAxis= us-gaap_MinimumMember |   |
| Benefit Obligations | Pension Plan | Maximum                                   |                                                                                                                                                                                                                                                                                                                                                                      |   |   |
| **Schedule of Benefit Obligations Weighted Average Assumptions**               |                                                                                                                                                                                                                                                                                                                                                                      |   |   |
| Rate of compensation increase                                                  | 3.25%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease/ cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis= cinf_BenefitObligationsMember/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember/ us-gaap_RangeAxis= us-gaap_MaximumMember                           | 3.25%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease/ cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis= cinf_BenefitObligationsMember/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember/ us-gaap_RangeAxis= us-gaap_MaximumMember |   |
| Benefit Obligations | Supplemental Employee Retirement Plan                    |                                                                                                                                                                                                                                                                                                                                                                      |   |   |
| **Schedule of Benefit Obligations Weighted Average Assumptions**               |                                                                                                                                                                                                                                                                                                                                                                      |   |   |
| Discount rate                                                                  | 4.05%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate/ cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis= cinf_BenefitObligationsMember/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember                                                             | 4.80%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate/ cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis= cinf_BenefitObligationsMember/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember |   |
| Benefit Obligations | Supplemental Employee Retirement Plan | Minimum          |                                                                                                                                                                                                                                                                                                                                                                      |   |   |
| **Schedule of Benefit Obligations Weighted Average Assumptions**               |                                                                                                                                                                                                                                                                                                                                                                      |   |   |
| Rate of compensation increase                                                  | 2.75%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease/ cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis= cinf_BenefitObligationsMember/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember/ us-gaap_RangeAxis= us-gaap_MinimumMember     | 2.75%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease/ cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis= cinf_BenefitObligationsMember/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember/ us-gaap_RangeAxis= us-gaap_MinimumMember |   |
| Benefit Obligations | Supplemental Employee Retirement Plan | Maximum          |                                                                                                                                                                                                                                                                                                                                                                      |   |   |
| **Schedule of Benefit Obligations Weighted Average Assumptions**               |                                                                                                                                                                                                                                                                                                                                                                      |   |   |
| Rate of compensation increase                                                  | 3.25%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease/ cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis= cinf_BenefitObligationsMember/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember/ us-gaap_RangeAxis= us-gaap_MaximumMember     | 3.25%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease/ cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis= cinf_BenefitObligationsMember/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember/ us-gaap_RangeAxis= us-gaap_MaximumMember |   |
| Net Periodic Benefit Cost | Pension Plan                                       |                                                                                                                                                                                                                                                                                                                                                                      |   |   |
| **Schedule of Benefit Obligations Weighted Average Assumptions**               |                                                                                                                                                                                                                                                                                                                                                                      |   |   |
| Discount rate                                                                  | 5.15%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate/ cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis= cinf_NetPeriodicBenefitCostMember/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember                                                                               | 4.20%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate/ cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis= cinf_NetPeriodicBenefitCostMember/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember | 5.10%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate/ cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis= cinf_NetPeriodicBenefitCostMember/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember |
| Expected return on plan assets                                                 | 7.25%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets/ cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis= cinf_NetPeriodicBenefitCostMember/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember                                                             | 7.50%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets/ cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis= cinf_NetPeriodicBenefitCostMember/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember | 7.50%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets/ cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis= cinf_NetPeriodicBenefitCostMember/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember |
| Net Periodic Benefit Cost | Pension Plan | Minimum                             |                                                                                                                                                                                                                                                                                                                                                                      |   |   |
| **Schedule of Benefit Obligations Weighted Average Assumptions**               |                                                                                                                                                                                                                                                                                                                                                                      |   |   |
| Rate of compensation increase                                                  | 2.75%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease/ cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis= cinf_NetPeriodicBenefitCostMember/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember/ us-gaap_RangeAxis= us-gaap_MinimumMember                       | 2.75%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease/ cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis= cinf_NetPeriodicBenefitCostMember/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember/ us-gaap_RangeAxis= us-gaap_MinimumMember | 3.50%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease/ cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis= cinf_NetPeriodicBenefitCostMember/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember/ us-gaap_RangeAxis= us-gaap_MinimumMember |
| Net Periodic Benefit Cost | Pension Plan | Maximum                             |                                                                                                                                                                                                                                                                                                                                                                      |   |   |
| **Schedule of Benefit Obligations Weighted Average Assumptions**               |                                                                                                                                                                                                                                                                                                                                                                      |   |   |
| Rate of compensation increase                                                  | 3.25%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease/ cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis= cinf_NetPeriodicBenefitCostMember/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember/ us-gaap_RangeAxis= us-gaap_MaximumMember                       | 3.25%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease/ cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis= cinf_NetPeriodicBenefitCostMember/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember/ us-gaap_RangeAxis= us-gaap_MaximumMember | 5.50%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease/ cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis= cinf_NetPeriodicBenefitCostMember/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_PensionPlansDefinedBenefitMember/ us-gaap_RangeAxis= us-gaap_MaximumMember |
| Net Periodic Benefit Cost | Supplemental Employee Retirement Plan              |                                                                                                                                                                                                                                                                                                                                                                      |   |   |
| **Schedule of Benefit Obligations Weighted Average Assumptions**               |                                                                                                                                                                                                                                                                                                                                                                      |   |   |
| Discount rate                                                                  | 4.80%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate/ cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis= cinf_NetPeriodicBenefitCostMember/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember                                                         | 3.95%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate/ cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis= cinf_NetPeriodicBenefitCostMember/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember | 4.75%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate/ cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis= cinf_NetPeriodicBenefitCostMember/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember |
| Net Periodic Benefit Cost | Supplemental Employee Retirement Plan | Minimum    |                                                                                                                                                                                                                                                                                                                                                                      |   |   |
| **Schedule of Benefit Obligations Weighted Average Assumptions**               |                                                                                                                                                                                                                                                                                                                                                                      |   |   |
| Rate of compensation increase                                                  | 2.75%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease/ cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis= cinf_NetPeriodicBenefitCostMember/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember/ us-gaap_RangeAxis= us-gaap_MinimumMember | 2.75%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease/ cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis= cinf_NetPeriodicBenefitCostMember/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember/ us-gaap_RangeAxis= us-gaap_MinimumMember | 3.50%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease/ cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis= cinf_NetPeriodicBenefitCostMember/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember/ us-gaap_RangeAxis= us-gaap_MinimumMember |
| Net Periodic Benefit Cost | Supplemental Employee Retirement Plan | Maximum    |                                                                                                                                                                                                                                                                                                                                                                      |   |   |
| **Schedule of Benefit Obligations Weighted Average Assumptions**               |                                                                                                                                                                                                                                                                                                                                                                      |   |   |
| Rate of compensation increase                                                  | 3.25%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease/ cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis= cinf_NetPeriodicBenefitCostMember/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember/ us-gaap_RangeAxis= us-gaap_MaximumMember | 3.25%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease/ cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis= cinf_NetPeriodicBenefitCostMember/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember/ us-gaap_RangeAxis= us-gaap_MaximumMember | 5.50%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease/ cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis= cinf_NetPeriodicBenefitCostMember/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis= us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember/ us-gaap_RangeAxis= us-gaap_MaximumMember |

| X                                                                                                                                                                                             |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**cinf_ScheduleOfBenefitObligationsWeightedAverageAssumptionsLineItems**Namespace Prefix:**cinf_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The interest rate used to adjust for the time value of money.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(1) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920
+ Details**Name:**us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostDiscountRate**Namespace Prefix:**us-gaap_**Data Type:**num:percentItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
An assumption as to the rate of return on plan assets reflecting the average rate of earnings expected on the funds invested or to be invested to provide for the benefits included in the benefit obligation.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 30 -Glossary Expected Long-Term Rate of Return on Plan Assets -URI http://asc.fasb.org/extlink&oid=6512013Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(3) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920
+ Details**Name:**us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostExpectedLongTermReturnOnAssets**Namespace Prefix:**us-gaap_**Data Type:**num:percentItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Expected rate of compensation increases (for pay-related plans).
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(2) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920
+ Details**Name:**us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingNetPeriodicBenefitCostRateOfCompensationIncrease**Namespace Prefix:**us-gaap_**Data Type:**num:percentItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                        |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis=cinf_BenefitObligationsMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                            |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**cinf_DefinedBenefitPlanByBenefitPlanCategoriesAxis=cinf_NetPeriodicBenefitCostMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |