XML 95 R82.htm IDEA: XBRL DOCUMENT
v3.22.4

Claim and Claim Adjustment Expense Reserves and Future Policy Benefit Reserves (Specialty - Surety - Net Strengthening or Releasing of Prior Accident Year Reserves) (Details) - Specialty - USD ($) $ in Millions | 12 Months Ended | 24 Months Ended | 36 Months Ended | 48 Months Ended | 60 Months Ended | 72 Months Ended | 84 Months Ended | 96 Months Ended | 108 Months Ended | 120 Months Ended
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2022 | Dec. 31, 2022 | Dec. 31, 2022 | Dec. 31, 2022 | Dec. 31, 2022 | Dec. 31, 2022 | Dec. 31, 2022 | Dec. 31, 2022 | Dec. 31, 2022
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total | $ (83) | $ (73) | $ (69) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Surety |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cumulative Number of Claims | (83) | (75) | (66) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total net development for accident years prior to 2013 | 0 | 2 | (3) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total unallocated claim adjustment expense development | 0 | 0 | 0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total | (83) | (73) | (69) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Surety | 2013 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cumulative Number of Claims | 0 | 0 | (1) | $ (4) | $ (4) | $ (15) | $ (9) | $ (6) | $ 1 |  |  |  |  |  |  |  |  | $ (38)
Surety | 2014 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cumulative Number of Claims | (1) | (2) | 0 | (15) | (9) | (25) | (30) | $ 1 |  |  |  |  |  |  |  |  | $ (81) |
Surety | 2015 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cumulative Number of Claims | (8) | (5) | (5) | (16) | (25) | (27) | $ 0 |  |  |  |  |  |  |  |  | $ (86) |  |
Surety | 2016 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cumulative Number of Claims | (6) | (3) | (17) | (25) | (15) | $ 0 |  |  |  |  |  |  |  |  | $ (66) |  |  |
Surety | 2017 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cumulative Number of Claims | (5) | (13) | (19) | (12) | $ (5) |  |  |  |  |  |  |  |  | $ (54) |  |  |  |
Surety | 2018 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cumulative Number of Claims | (6) | (29) | (17) | $ (6) |  |  |  |  |  |  |  |  | $ (58) |  |  |  |  |
Surety | 2019 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cumulative Number of Claims | (11) | (14) | $ (7) |  |  |  |  |  |  |  |  | $ (32) |  |  |  |  |  |
Surety | 2020 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cumulative Number of Claims | (38) | $ (9) |  |  |  |  |  |  |  |  | $ (47) |  |  |  |  |  |  |
Surety | 2022 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Claims Development [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cumulative Number of Claims | $ (8) |  |  |  |  |  |  |  |  | $ (8) |  |  |  |  |  |  |  |

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

X
- Definition Unallocated Claim Adjustment Expense Development + References No definition available. + Details
Name: | cna_UnallocatedClaimAdjustmentExpenseDevelopment
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_ClaimsDevelopmentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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

X
- Details
Name: | srt_ProductOrServiceAxis=cna_SuretyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortdurationInsuranceContractsAccidentYear2013Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortdurationInsuranceContractsAccidentYear2014Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortdurationInsuranceContractsAccidentYear2015Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortdurationInsuranceContractsAccidentYear2016Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortDurationInsuranceContractsAccidentYear2017Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortDurationInsuranceContractsAccidentYear2018Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ShortdurationInsuranceContractsAccidentYearAxis=us-gaap_ShortDurationInsuranceContractAccidentYear2019Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

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