Life Policy and Investment Contract Reserves (Narrative) (Details) - USD ($)	3 Months Ended
Mar. 31, 2023	Mar. 31, 2022
Life policy reserves:
Liability for Future Policy Benefit, Activity [Line Items]
Discount Rate Assumption Changes included in Impact of flooring at Cohort Level	$ 5,000,000	$ 6,000,000
Life Insurance Segment
Liability for Future Policy Benefit, Activity [Line Items]
Liability for Future Policy Benefit, Adverse Development, Expense	$ 0

Discount Rate Assumption Changes included in Impact of flooring at Cohort Level

No definition available.

Name:	cinf_DiscountRateAssumptionChangesIncludedInImpactOfFlooringAtCohortLevel
Namespace Prefix:	cinf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 29E
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480046/944-40-55-29E

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480081/944-40-50-6

+ Details

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

- Definition

Amount of expense for adverse development on liability of future policy benefit from net premium exceeding gross premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 65
-Paragraph 2
-Subparagraph (g)(2)(iii)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480016/944-40-65-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480081/944-40-50-6

+ Details

Name:	us-gaap_LiabilityForFuturePolicyBenefitAdverseDevelopmentExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_EquitySecuritiesByIndustryAxis=cinf_LifePolicyReservesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_EquitySecuritiesByIndustryAxis=cinf_LifeInsuranceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: