XML 135 R120.htm IDEA: XBRL DOCUMENT
v3.25.0.1

Reinsurance (Narrative) (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022 | Feb. 05, 2021
Ceded Credit Risk [Line Items] |  |  |  |
Funds held under reinsurance agreements, liability | $ 3,400 | $ 3,600 |  | $ 690
Largest recoverable from single reinsurer | 6,051 | 5,412 |  |
Reinsurance recoveries reported in insurance claims and policyholders' benefits reported on the Consolidated Statement of Operations | 3,450 | 2,772 | $ 2,631 |
Subsidiaries of Berkshire Hathaway Group |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |
Largest recoverable from single reinsurer | 1,800 |  |  |
Cavello Bay Reinsurance Limited |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |
Largest recoverable from single reinsurer | 559 |  |  |
Swiss Reinsurance Group |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |
Largest recoverable from single reinsurer | 371 |  |  |
Significant Captive Program |  |  |  |
Ceded Credit Risk [Line Items] |  |  |  |
Direct and ceded earned premiums | 2,653 | 2,907 | 3,270 |
Reinsurance recoveries reported in insurance claims and policyholders' benefits reported on the Consolidated Statement of Operations | $ 1,730 | $ 1,512 | $ 1,796 |

X
- Definition Direct and ceded earned premiums related to business that is one hundred percent reinsured as a result of a significant captive program + References No definition available. + Details
Name: | cna_DirectAndCededEarnedPremiumsRelatedToBusinessThatIsOneHundredPercentReinsuredAsResultOfSignificantCaptiveProgram
Namespace Prefix: | cna_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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 Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 825 -Name Accounting Standards Codification -Section 50 -Paragraph 1B -Publisher FASB -URI https://asc.fasb.org/1943274/2147477351/944-825-50-1B + Details
Name: | us-gaap_CededCreditRiskLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of funds held as security for payments to be received under reinsurance contracts. + References No definition available. + Details
Name: | us-gaap_FundsHeldUnderReinsuranceAgreementsLiability
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of reduction of provision for policy benefits and costs incurred for policies ceded. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479838/944-20-50-3 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(5)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1 + Details
Name: | us-gaap_ReinsuranceEffectOnClaimsAndBenefitsIncurredAmountCeded
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount, after valuation allowance, recoverable under reinsurance contracts including premium paid under reinsurance contracts. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, premium paid, policy benefits and policy reserves. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479838/944-20-50-5 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 310 -Name Accounting Standards Codification -Section 45 -Paragraph 5 -Publisher FASB -URI https://asc.fasb.org/1943274/2147477409/944-310-45-5 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)(6)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1 + Details
Name: | us-gaap_ReinsuranceRecoverables
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_CededCreditRiskAxis=cna_SubsidiariesOfBerkshireHathawayGroupMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CededCreditRiskAxis=cna_CavelloBayReinsuranceLimitedMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CededCreditRiskAxis=cna_SwissReinsuranceGroupMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CededCreditRiskAxis=cna_SignificantCaptiveProgramMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |