| **Investments (Fair Values And Unrealized Losses By Investment Category And By The Duration Of The Securities' Continuous Unrealized Loss Position) (Details) - USD ($) $ in Millions** | Dec. 31, 2022 | Dec. 31, 2021 |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------|---------------|
| **Investments, Unrealized Loss Position**                                                                                                                                               |          |          |
| Total Unrealized Losses                                                                                                                                                                 | $ 908         | $ 16          |
| Corporate Securities                                                                                                                                                                    |          |          |
| **Investments, Unrealized Loss Position**                                                                                                                                               |          |          |
| Total Unrealized Losses                                                                                                                                                                 | 580           | 13            |
| States, Municipalities and Political Subdivisions                                                                                                                                       |          |          |
| **Investments, Unrealized Loss Position**                                                                                                                                               |          |          |
| Total Unrealized Losses                                                                                                                                                                 | 303           | 3             |
| Commercial Mortgage Backed Securities                                                                                                                                                   |          |          |
| **Investments, Unrealized Loss Position**                                                                                                                                               |          |          |
| Total Unrealized Losses                                                                                                                                                                 | 16            | 0             |
| United States Government                                                                                                                                                                |          |          |
| **Investments, Unrealized Loss Position**                                                                                                                                               |          |          |
| Total Unrealized Losses                                                                                                                                                                 | 5             | 0             |
| Government-Sponsored Enterprises                                                                                                                                                        |          |          |
| **Investments, Unrealized Loss Position**                                                                                                                                               |          |          |
| Total Unrealized Losses                                                                                                                                                                 | 3             | 0             |
| Fixed Maturities                                                                                                                                                                        |          |          |
| **Investments, Unrealized Loss Position**                                                                                                                                               |          |          |
| Less than 12 months fair value                                                                                                                                                          | 8,760         | 1,047         |
| Less than 12 Months, Unrealized losses                                                                                                                                                  | 706           | 15            |
| 12 months or more fair value                                                                                                                                                            | 800           | 28            |
| 12 Months or more, unrealized losses                                                                                                                                                    | 202           | 1             |
| Total fair value                                                                                                                                                                        | 9,560         | 1,075         |
| Total Unrealized Losses                                                                                                                                                                 | 908           | 16            |
| Fixed Maturities | Corporate Securities                                                                                                                                                 |          |          |
| **Investments, Unrealized Loss Position**                                                                                                                                               |          |          |
| Less than 12 months fair value                                                                                                                                                          | 5,651         | 861           |
| Less than 12 Months, Unrealized losses                                                                                                                                                  | 412           | 13            |
| 12 months or more fair value                                                                                                                                                            | 661           | 15            |
| 12 Months or more, unrealized losses                                                                                                                                                    | 168           | 0             |
| Total fair value                                                                                                                                                                        | 6,312         | 876           |
| Total Unrealized Losses                                                                                                                                                                 | 580           | 13            |
| Fixed Maturities | States, Municipalities and Political Subdivisions                                                                                                                    |          |          |
| **Investments, Unrealized Loss Position**                                                                                                                                               |          |          |
| Less than 12 months fair value                                                                                                                                                          | 2,600         | 105           |
| Less than 12 Months, Unrealized losses                                                                                                                                                  | 274           | 2             |
| 12 months or more fair value                                                                                                                                                            | 77            | 2             |
| 12 Months or more, unrealized losses                                                                                                                                                    | 29            | 1             |
| Total fair value                                                                                                                                                                        | 2,677         | 107           |
| Total Unrealized Losses                                                                                                                                                                 | 303           | 3             |
| Fixed Maturities | Commercial Mortgage Backed Securities                                                                                                                                |          |          |
| **Investments, Unrealized Loss Position**                                                                                                                                               |          |          |
| Less than 12 months fair value                                                                                                                                                          | 215           | 10            |
| Less than 12 Months, Unrealized losses                                                                                                                                                  | 13            | 0             |
| 12 months or more fair value                                                                                                                                                            | 14            | 11            |
| 12 Months or more, unrealized losses                                                                                                                                                    | 3             | 0             |
| Total fair value                                                                                                                                                                        | 229           | 21            |
| Total Unrealized Losses                                                                                                                                                                 | 16            | 0             |
| Fixed Maturities | United States Government                                                                                                                                             |          |          |
| **Investments, Unrealized Loss Position**                                                                                                                                               |          |          |
| Less than 12 months fair value                                                                                                                                                          | 146           | 48            |
| Less than 12 Months, Unrealized losses                                                                                                                                                  | 3             | 0             |
| 12 months or more fair value                                                                                                                                                            | 41            | 0             |
| 12 Months or more, unrealized losses                                                                                                                                                    | 2             | 0             |
| Total fair value                                                                                                                                                                        | 187           | 48            |
| Total Unrealized Losses                                                                                                                                                                 | 5             | 0             |
| Fixed Maturities | Government-Sponsored Enterprises                                                                                                                                     |          |          |
| **Investments, Unrealized Loss Position**                                                                                                                                               |          |          |
| Less than 12 months fair value                                                                                                                                                          | 123           | 7             |
| Less than 12 Months, Unrealized losses                                                                                                                                                  | 3             | 0             |
| 12 months or more fair value                                                                                                                                                            | 3             | 0             |
| 12 Months or more, unrealized losses                                                                                                                                                    | 0             | 0             |
| Total fair value                                                                                                                                                                        | 126           | 7             |
| Total Unrealized Losses                                                                                                                                                                 | 3             | 0             |
| Fixed Maturities | Foreign government                                                                                                                                                   |          |          |
| **Investments, Unrealized Loss Position**                                                                                                                                               |          |          |
| Less than 12 months fair value                                                                                                                                                          | 25            | 16            |
| Less than 12 Months, Unrealized losses                                                                                                                                                  | 1             | 0             |
| 12 months or more fair value                                                                                                                                                            | 4             | 0             |
| 12 Months or more, unrealized losses                                                                                                                                                    | 0             | 0             |
| Total fair value                                                                                                                                                                        | 29            | 16            |
| Total Unrealized Losses                                                                                                                                                                 | $ 1           | $ 0           |

| X                                                                                                                                                                                                                                                                              |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Investments, Unrealized Loss Position [Line Items]
+ References
No definition available.
+ Details**Name:**cinf_InvestmentsUnrealizedLossPositionLineItems**Namespace Prefix:**cinf_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).
+ References
Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27161-111563
+ Details**Name:**us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.
+ References
Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 5 -URI https://asc.fasb.org/extlink&oid=124269663&loc=SL82922890-210455Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27337-111563Reference 3: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 55 -Paragraph 8 -URI https://asc.fasb.org/extlink&oid=121590138&loc=SL82922954-210456
+ Details**Name:**us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset.
+ References
Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27337-111563Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 5 -URI https://asc.fasb.org/extlink&oid=124269663&loc=SL82922890-210455
+ Details**Name:**us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.
+ References
Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27337-111563Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 5 -URI https://asc.fasb.org/extlink&oid=124269663&loc=SL82922890-210455Reference 3: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 55 -Paragraph 8 -URI https://asc.fasb.org/extlink&oid=121590138&loc=SL82922954-210456
+ Details**Name:**us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12Months**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.
+ References
Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 5 -URI https://asc.fasb.org/extlink&oid=124269663&loc=SL82922890-210455Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27337-111563
+ Details**Name:**us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position without allowance for credit loss.
+ References
Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (a)(1) -URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27290-111563Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 50 -Paragraph 4 -Subparagraph (a)(1) -URI https://asc.fasb.org/extlink&oid=124269663&loc=SL82922888-210455Reference 3: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 30 -Section 55 -Paragraph 8 -URI https://asc.fasb.org/extlink&oid=121590138&loc=SL82922954-210456
+ Details**Name:**us-gaap_DebtSecuritiesAvailableForSaleUnrealizedLossPosition**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                             |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_FinancialInstrumentAxis=us-gaap_CorporateBondSecuritiesMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                      |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_FinancialInstrumentAxis=us-gaap_USStatesAndPoliticalSubdivisionsMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                        |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_FinancialInstrumentAxis=us-gaap_CommercialMortgageBackedSecuritiesMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                        |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_FinancialInstrumentAxis=us-gaap_USGovernmentAgenciesDebtSecuritiesMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                    |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_FinancialInstrumentAxis=us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                               |
|-------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_InvestmentTypeAxis=us-gaap_DebtSecuritiesMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                     |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_FinancialInstrumentAxis=us-gaap_ForeignGovernmentDebtSecuritiesMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |