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.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 9E
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480046/944-40-55-9E

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 4E
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480081/944-40-50-4E

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 4D
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480081/944-40-50-4D

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 4B
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480081/944-40-50-4B

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 4B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480081/944-40-50-4B

+ Details

Name:	us-gaap_ClaimsDevelopmentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- 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

+ Details

Name:	us-gaap_ShortdurationInsuranceContractsCumulativePaidClaimsAndAllocatedClaimAdjustmentExpenseNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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

+ Details

Name:	us-gaap_ShortdurationInsuranceContractsIncurredButNotReportedIbnrClaimsLiabilityNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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

+ Details

Name:	us-gaap_ShortdurationInsuranceContractsIncurredClaimsAndAllocatedClaimAdjustmentExpenseNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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

+ Details

Name:	us-gaap_ShortdurationInsuranceContractsLiabilityForUnpaidClaimsAndAllocatedClaimAdjustmentExpenseNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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

+ Details

Name:	us-gaap_ShortdurationInsuranceContractsLiabilityForUnpaidClaimsAndAllocatedClaimAdjustmentExpenseNetNotSeparatelyPresented
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Cumulative number of reported claims for short-duration insurance contracts.

+ References

+ Details

Name:	us-gaap_ShortdurationInsuranceContractsNumberOfReportedClaims
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	srt_ProductOrServiceAxis=cinf_PersonalAutoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=cinf_PersonalLinesInsuranceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortDurationInsuranceContractAccidentYear2020Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortDurationInsuranceContractAccidentYear2021Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortDurationInsuranceContractAccidentYear2022Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortDurationInsuranceContractAccidentYear2023Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortDurationInsuranceContractAccidentYear2024Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Property Casualty Loss and Loss Expense - Claims Development - Personal Auto (Details) reported_claim in Thousands, $ in Millions	Dec. 31, 2024 USD ($) reported_claim	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Claims Development
Incurred losses and ALAE, net of reinsurance for the years ended December 31,	$ 3,589
Liabilities for loss and ALAE, net of reinsurance	9,416
Personal Auto \| Personal Insurance
Claims Development
Incurred losses and ALAE, net of reinsurance for the years ended December 31,	2,115
Cumulative paid losses and ALAE, net of reinsurance	1,739
All outstanding liabilities before, net of reinsurance	13
Liabilities for loss and ALAE, net of reinsurance	389
2020 \| Personal Auto \| Personal Insurance
Claims Development
Incurred losses and ALAE, net of reinsurance for the years ended December 31,	276	$ 277	$ 277	$ 281	$ 305
Total of incurred but not reported liabilities plus expected development on reported losses	$ 1
Cumulative number of reported claims \| reported_claim	71
Cumulative paid losses and ALAE, net of reinsurance	$ 271	264	248	225	$ 186
2021 \| Personal Auto \| Personal Insurance
Claims Development
Incurred losses and ALAE, net of reinsurance for the years ended December 31,	344	342	343	350
Total of incurred but not reported liabilities plus expected development on reported losses	$ 3
Cumulative number of reported claims \| reported_claim	80
Cumulative paid losses and ALAE, net of reinsurance	$ 325	304	278	$ 219
2022 \| Personal Auto \| Personal Insurance
Claims Development
Incurred losses and ALAE, net of reinsurance for the years ended December 31,	429	418	427
Total of incurred but not reported liabilities plus expected development on reported losses	$ 10
Cumulative number of reported claims \| reported_claim	86
Cumulative paid losses and ALAE, net of reinsurance	$ 382	349	$ 277
2023 \| Personal Auto \| Personal Insurance
Claims Development
Incurred losses and ALAE, net of reinsurance for the years ended December 31,	474	466
Total of incurred but not reported liabilities plus expected development on reported losses	$ 25
Cumulative number of reported claims \| reported_claim	92
Cumulative paid losses and ALAE, net of reinsurance	$ 389	$ 304
2024 \| Personal Auto \| Personal Insurance
Claims Development
Incurred losses and ALAE, net of reinsurance for the years ended December 31,	592
Total of incurred but not reported liabilities plus expected development on reported losses	$ 106
Cumulative number of reported claims \| reported_claim	100
Cumulative paid losses and ALAE, net of reinsurance	$ 372