| **Claims Development - Homeowner (Details) reported_claim in Thousands, $ in Millions**     | Dec. 31, 2022 USD ($) reported_claim | Dec. 31, 2021 USD ($) | Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($) |
|---------------------------------------------------------------------------------------------|--------------------------------------|-----------------------|-----------------------|-----------------------|-----------------------|
| **Claims Development**                                                                      |                                 |                  |                  |                  |                  |
| Incurred losses and ALAE, net of reinsurance for the years ended December 31,               | $ 3,312                              |                  |                  |                  |                  |
| Liabilities for loss and ALAE, net of reinsurance                                           | 7,967                                |                  |                  |                  |                  |
| Home Owner Line | Personal Insurance                                                        |                                 |                  |                  |                  |                  |
| **Claims Development**                                                                      |                                 |                  |                  |                  |                  |
| Incurred losses and ALAE, net of reinsurance for the years ended December 31,               | 2,275                                |                  |                  |                  |                  |
| Cumulative paid losses and ALAE, net of reinsurance                                         | 1,952                                |                  |                  |                  |                  |
| All outstanding liabilities before, net of reinsurance                                      | 6                                    |                  |                  |                  |                  |
| Liabilities for loss and ALAE, net of reinsurance                                           | 329                                  |                  |                  |                  |                  |
| 2018 | Home Owner Line | Personal Insurance                                                 |                                 |                  |                  |                  |                  |
| **Claims Development**                                                                      |                                 |                  |                  |                  |                  |
| Incurred losses and ALAE, net of reinsurance for the years ended December 31,               | 386                                  | $ 388                 | $ 387                 | $ 386                 | $ 370                 |
| Total of incurred but not reported liabilities plus expected development on reported losses | $ 1                                  |                  |                  |                  |                  |
| Cumulative number of reported claims | reported_claim                                       | 24                                   |                  |                  |                  |                  |
| Cumulative paid losses and ALAE, net of reinsurance                                         | $ 384                                | 381                   | 378                   | 368                   | $ 268                 |
| 2019 | Home Owner Line | Personal Insurance                                                 |                                 |                  |                  |                  |                  |
| **Claims Development**                                                                      |                                 |                  |                  |                  |                  |
| Incurred losses and ALAE, net of reinsurance for the years ended December 31,               | 418                                  | 422                   | 421                   | 432                   |                  |
| Total of incurred but not reported liabilities plus expected development on reported losses | $ 2                                  |                  |                  |                  |                  |
| Cumulative number of reported claims | reported_claim                                       | 22                                   |                  |                  |                  |                  |
| Cumulative paid losses and ALAE, net of reinsurance                                         | $ 411                                | 407                   | 391                   | $ 303                 |                  |
| 2020 | Home Owner Line | Personal Insurance                                                 |                                 |                  |                  |                  |                  |
| **Claims Development**                                                                      |                                 |                  |                  |                  |                  |
| Incurred losses and ALAE, net of reinsurance for the years ended December 31,               | 470                                  | 475                   | 497                   |                  |                  |
| Total of incurred but not reported liabilities plus expected development on reported losses | $ 7                                  |                  |                  |                  |                  |
| Cumulative number of reported claims | reported_claim                                       | 23                                   |                  |                  |                  |                  |
| Cumulative paid losses and ALAE, net of reinsurance                                         | $ 453                                | 434                   | $ 326                 |                  |                  |
| 2021 | Home Owner Line | Personal Insurance                                                 |                                 |                  |                  |                  |                  |
| **Claims Development**                                                                      |                                 |                  |                  |                  |                  |
| Incurred losses and ALAE, net of reinsurance for the years ended December 31,               | 449                                  | 495                   |                  |                  |                  |
| Total of incurred but not reported liabilities plus expected development on reported losses | $ 15                                 |                  |                  |                  |                  |
| Cumulative number of reported claims | reported_claim                                       | 19                                   |                  |                  |                  |                  |
| Cumulative paid losses and ALAE, net of reinsurance                                         | $ 405                                | $ 285                 |                  |                  |                  |
| 2022 | Home Owner Line | Personal Insurance                                                 |                                 |                  |                  |                  |                  |
| **Claims Development**                                                                      |                                 |                  |                  |                  |                  |
| Incurred losses and ALAE, net of reinsurance for the years ended December 31,               | 552                                  |                  |                  |                  |                  |
| Total of incurred but not reported liabilities plus expected development on reported losses | $ 120                                |                  |                  |                  |                  |
| Cumulative number of reported claims | reported_claim                                       | 17                                   |                  |                  |                  |                  |
| Cumulative paid losses and ALAE, net of reinsurance                                         | $ 299                                |                  |                  |                  |                  |

| X                                                                                                                                                                                                                                                                                                                                                                                                                  |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.
+ References
No definition available.
+ Details**Name:**us-gaap_ClaimsDevelopmentLineItems**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount, after reinsurance, of paid claims and allocated claim adjustment expense used in claims development for short-duration insurance contracts. Excludes unallocated claim adjustment expense.
+ References
Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 4B -Subparagraph (b) -URI https://asc.fasb.org/extlink&oid=116884468&loc=SL65671311-158438
+ Details**Name:**us-gaap_ShortdurationInsuranceContractsCumulativePaidClaimsAndAllocatedClaimAdjustmentExpenseNet**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Undiscounted amount, after reinsurance, of incurred-but-not-reported (IBNR) liabilities plus expected development on reported claims, for claims and allocated claim adjustment expense for short-duration insurance contracts. Excludes unallocated claim adjustment expense.
+ References
Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 4E -URI https://asc.fasb.org/extlink&oid=116884468&loc=SL65671321-158438Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 4D -Subparagraph (a) -URI https://asc.fasb.org/extlink&oid=116884468&loc=SL65671317-158438
+ Details**Name:**us-gaap_ShortdurationInsuranceContractsIncurredButNotReportedIbnrClaimsLiabilityNet**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Undiscounted amount, after reinsurance, of incurred claims and allocated claim adjustment expense used in claims development for short-duration insurance contracts. Excludes unallocated claim adjustment expense.
+ References
Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 4B -Subparagraph (a) -URI https://asc.fasb.org/extlink&oid=116884468&loc=SL65671311-158438
+ Details**Name:**us-gaap_ShortdurationInsuranceContractsIncurredClaimsAndAllocatedClaimAdjustmentExpenseNet**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Undiscounted amount, after reinsurance, of the liability for unpaid claims and allocated claim adjustment expense for short-duration insurance contracts. Excludes unallocated claim adjustment expense.
+ References
Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 4C -URI https://asc.fasb.org/extlink&oid=116884468&loc=SL65671315-158438Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 4B -URI https://asc.fasb.org/extlink&oid=116884468&loc=SL65671311-158438
+ Details**Name:**us-gaap_ShortdurationInsuranceContractsLiabilityForUnpaidClaimsAndAllocatedClaimAdjustmentExpenseNet**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Undiscounted amount, after reinsurance, of the liability for unpaid claims and allocated claim adjustment expense for short-duration insurance contracts for accident years not separately presented in claim development information. Excludes unallocated claim adjustment expense.
+ References
Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 4B -URI https://asc.fasb.org/extlink&oid=116884468&loc=SL65671311-158438
+ Details**Name:**us-gaap_ShortdurationInsuranceContractsLiabilityForUnpaidClaimsAndAllocatedClaimAdjustmentExpenseNetNotSeparatelyPresented**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Cumulative number of reported claims for short-duration insurance contracts.
+ References
Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 4D -Subparagraph (b) -URI https://asc.fasb.org/extlink&oid=116884468&loc=SL65671317-158438
+ Details**Name:**us-gaap_ShortdurationInsuranceContractsNumberOfReportedClaims**Namespace Prefix:**us-gaap_**Data Type:**xbrli:integerItemType**Balance Type:**na**Period Type:**instant |
| X                                                                                                                                            |
|----------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**srt_ProductOrServiceAxis=cinf_HomeOwnerSegmentMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                               |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_StatementBusinessSegmentsAxis=cinf_PersonalLinesInsuranceMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                                             |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortDurationInsuranceContractsAccidentYear2018Member**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                                            |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortDurationInsuranceContractAccidentYear2019Member**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                                            |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortDurationInsuranceContractAccidentYear2020Member**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                                            |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortDurationInsuranceContractAccidentYear2021Member**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                                            |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortDurationInsuranceContractAccidentYear2022Member**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |