Changes in Policyholders' Account Balances (Details) - Investment contract reserves - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Deferred Fixed Annuity
Policyholder Account Balance [Roll Forward]
Balance, beginning of period	$ 656	$ 734	$ 763
Premiums received	35	44	29
Policy charges	0	0	0
Surrenders and withdrawals	(105)	(130)	(62)
Benefit payments	(13)	(14)	(18)
Interest credited	22	22	22
Balance, end of period	$ 595	$ 656	$ 734
Weighted average crediting rate	3.68%	3.51%	3.36%
Net amount at risk	$ 0	$ 0	$ 0
Cash surrender value	589	651	729
Universal Life
Policyholder Account Balance [Roll Forward]
Balance, beginning of period	457	457	454
Premiums received	37	39	39
Policy charges	(40)	(39)	(39)
Surrenders and withdrawals	(12)	(13)	(11)
Benefit payments	(5)	(6)	(5)
Interest credited	19	19	19
Balance, end of period	$ 456	$ 457	$ 457
Weighted average crediting rate	4.39%	4.30%	4.27%
Net amount at risk	$ 3,833	$ 3,949	$ 4,082
Cash surrender value	$ 427	$ 426	$ 424

Amount of cash to be paid to policyholder upon termination and surrender of long-duration contract issued by insurance entity.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 7A
-Subparagraph (b)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480081/944-40-50-7A

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 29F
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480046/944-40-55-29F

+ Details

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

- Definition

Amount of interest expense for allocation to policyholder account balance.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 7A
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480081/944-40-50-7A

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 29F
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480046/944-40-55-29F

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479868/944-20-45-2

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 13J
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480046/944-40-55-13J

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(6))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1

+ Details

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

- Definition

Amount of cash outflow to policyholder account balance from benefit payment.

+ References

+ Details

Name:	us-gaap_PolicyholderAccountBalanceBenefitPayment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of guaranteed benefit in excess of current account balance of policyholder account balance.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 7A
-Subparagraph (b)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480081/944-40-50-7A

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 29F
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480046/944-40-55-29F

+ Details

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

- Definition

Amount of decrease in liability for policyholder account balance from policy charge.

+ References

+ Details

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

- Definition

Amount of cash inflow to policyholder account balance from premium received.

+ References

+ Details

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

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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

- Definition

Amount of decrease in liability for policyholder account balance from contract redemption and withdrawal of funds.

+ References

+ Details

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

- Definition

Weighted-average crediting rate for liability for policyholder account balance, calculated at a point in time.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 7A
-Subparagraph (b)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480081/944-40-50-7A

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 29F
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480046/944-40-55-29F

+ Details

Name:	us-gaap_PolicyholderAccountBalanceWeightedAverageCreditingRate
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount due to policyholder. Includes, but is not limited to, unpaid policy dividend, retrospective refund, and undistributed earnings on participating business. Excludes future policy benefit and claim expense.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 7A
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480081/944-40-50-7A

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 7A
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480081/944-40-50-7A

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(14)(a))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 29F
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480046/944-40-55-29F

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 7A
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480081/944-40-50-7A

+ Details

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

- Details

Name:	srt_ProductOrServiceAxis=us-gaap_DeferredFixedAnnuityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	srt_ProductOrServiceAxis=us-gaap_UniversalLifeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: