XML 68 R55.htm IDEA: XBRL DOCUMENT
v3.25.2

Claim and Claim Adjustment Expense Reserves (International - Net prior year claim and allocated claim adjustment expense reserve development) (Details) - International - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2025 | Jun. 30, 2024 | Jun. 30, 2025 | Jun. 30, 2024
Liability for Claims and Claims Adjustment Expense [Line Items] |  |  |  |
Commercial | $ (3) | $ 6 | $ (3) | $ 6
Specialty | 4 | (9) | 4 | (9)
Other | (1) | 0 | (1) | 0
Total pretax (favorable) unfavorable development | $ 0 | $ (3) | $ 0 | $ (3)

X
- Definition Net prior year claim and allocated claim adjustment expense reserve development, Commercial Auto + References No definition available. + Details
Name: | cna_NetPriorYearClaimAndAllocatedClaimAdjustmentExpenseReserveDevelopmentCommercialAuto
Namespace Prefix: | cna_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development, Specialty + References No definition available. + Details
Name: | cna_NetPriorYearClaimAndAllocatedClaimAdjustmentExpenseReserveDevelopmentSpecialty
Namespace Prefix: | cna_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Net Prior Year Claim and Allocated Claim Adjustment Expense Reserve Development, Other Professional Liability + References No definition available. + Details
Name: | cna_NetPriorYearClaimandAllocatedClaimAdjustmentExpenseReserveDevelopmentOtherProfessionalLiability
Namespace Prefix: | cna_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Pretax (favorable) unfavorable net prior year claim and allocated claim adjustment expense reserve development, excluding Life & Group + References No definition available. + Details
Name: | cna_PretaxFavorableUnfavorableNetPriorYearClaimAndAllocatedClaimAdjustmentExpenseReserveDevelopmentExcludingLifeGroup
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 No definition available. + Details
Name: | us-gaap_LiabilityForClaimsAndClaimsAdjustmentExpenseLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=cna_InternationalSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |