XML 104 R91.htm IDEA: XBRL DOCUMENT
v3.22.4

Claim and Claim Adjustment Expense Reserves and Future Policy Benefit Reserves (Commercial - Workers' Compensation - Net Incurred Claims and Allocated Claim Adjustment Expenses) (Details) - Workers' Compensation - Commercial $ in Millions | Dec. 31, 2022 USD ($) claim | Dec. 31, 2021 USD ($) | Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($) | Dec. 31, 2014 USD ($) | Dec. 31, 2013 USD ($)
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred claims and allocated claim adjustment expense, net | $ 4,298 |  |  |  |  |  |  |  |  |
IBNR | 1,286 |  |  |  |  |  |  |  |  |
2013 |  |  |  |  |  |  |  |  |  |
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred claims and allocated claim adjustment expense, net | 537 | $ 548 | $ 552 | $ 561 | $ 582 | $ 593 | $ 618 | $ 592 | $ 572 | $ 537
IBNR | $ 82 |  |  |  |  |  |  |  |  |
Cumulative Number of Claims | claim | 38,979 |  |  |  |  |  |  |  |  |
2014 |  |  |  |  |  |  |  |  |  |
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred claims and allocated claim adjustment expense, net | $ 430 | 448 | 439 | 446 | 450 | 452 | 479 | 480 | $ 467 |
IBNR | $ 76 |  |  |  |  |  |  |  |  |
Cumulative Number of Claims | claim | 33,522 |  |  |  |  |  |  |  |  |
2015 |  |  |  |  |  |  |  |  |  |
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred claims and allocated claim adjustment expense, net | $ 353 | 372 | 382 | 394 | 408 | 406 | 431 | $ 422 |  |
IBNR | $ 80 |  |  |  |  |  |  |  |  |
Cumulative Number of Claims | claim | 31,899 |  |  |  |  |  |  |  |  |
2016 |  |  |  |  |  |  |  |  |  |
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred claims and allocated claim adjustment expense, net | $ 331 | 355 | 366 | 382 | 396 | 405 | $ 426 |  |  |
IBNR | $ 77 |  |  |  |  |  |  |  |  |
Cumulative Number of Claims | claim | 31,991 |  |  |  |  |  |  |  |  |
2017 |  |  |  |  |  |  |  |  |  |
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred claims and allocated claim adjustment expense, net | $ 399 | 402 | 400 | 421 | 432 | $ 440 |  |  |  |
IBNR | $ 81 |  |  |  |  |  |  |  |  |
Cumulative Number of Claims | claim | 33,130 |  |  |  |  |  |  |  |  |
2018 |  |  |  |  |  |  |  |  |  |
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred claims and allocated claim adjustment expense, net | $ 415 | 415 | 428 | 440 | $ 450 |  |  |  |  |
IBNR | $ 93 |  |  |  |  |  |  |  |  |
Cumulative Number of Claims | claim | 34,875 |  |  |  |  |  |  |  |  |
2019 |  |  |  |  |  |  |  |  |  |
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred claims and allocated claim adjustment expense, net | $ 436 | 437 | 449 | $ 452 |  |  |  |  |  |
IBNR | $ 105 |  |  |  |  |  |  |  |  |
Cumulative Number of Claims | claim | 34,324 |  |  |  |  |  |  |  |  |
2020 |  |  |  |  |  |  |  |  |  |
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred claims and allocated claim adjustment expense, net | $ 446 | 466 | $ 477 |  |  |  |  |  |  |
IBNR | $ 182 |  |  |  |  |  |  |  |  |
Cumulative Number of Claims | claim | 29,392 |  |  |  |  |  |  |  |  |
2021 |  |  |  |  |  |  |  |  |  |
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred claims and allocated claim adjustment expense, net | $ 454 | $ 468 |  |  |  |  |  |  |  |
IBNR | $ 202 |  |  |  |  |  |  |  |  |
Cumulative Number of Claims | claim | 29,886 |  |  |  |  |  |  |  |  |
2022 |  |  |  |  |  |  |  |  |  |
Short-duration Insurance Contracts, Net Incurred Claim and Claim Adjustment Expenses [Line Items] |  |  |  |  |  |  |  |  |  |
Incurred claims and allocated claim adjustment expense, net | $ 497 |  |  |  |  |  |  |  |  |
IBNR | $ 308 |  |  |  |  |  |  |  |  |
Cumulative Number of Claims | claim | 28,753 |  |  |  |  |  |  |  |  |

X
- Definition [Line Items] for Net Incurred Claim and Claim Adjustment Expense [Table] + References No definition available. + Details
Name: | cna_NetIncurredClaimandClaimAdjustmentExpenseLineItems
Namespace Prefix: | cna_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Undiscounted amount, after reinsurance, of incurred-but-not-reported (IBNR) liabilities plus expected development on reported claims, for claims and allocated claim adjustment expense for short-duration insurance contracts. Excludes unallocated claim adjustment expense. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 4E -URI https://asc.fasb.org/extlink&oid=116884468&loc=SL65671321-158438 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 4D -Subparagraph (a) -URI https://asc.fasb.org/extlink&oid=116884468&loc=SL65671317-158438 + Details
Name: | us-gaap_ShortdurationInsuranceContractsIncurredButNotReportedIbnrClaimsLiabilityNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Undiscounted amount, after reinsurance, of incurred claims and allocated claim adjustment expense used in claims development for short-duration insurance contracts. Excludes unallocated claim adjustment expense. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 4B -Subparagraph (a) -URI https://asc.fasb.org/extlink&oid=116884468&loc=SL65671311-158438 + Details
Name: | us-gaap_ShortdurationInsuranceContractsIncurredClaimsAndAllocatedClaimAdjustmentExpenseNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Cumulative number of reported claims for short-duration insurance contracts. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 4D -Subparagraph (b) -URI https://asc.fasb.org/extlink&oid=116884468&loc=SL65671317-158438 + Details
Name: | us-gaap_ShortdurationInsuranceContractsNumberOfReportedClaims
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

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

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=cna_CommercialSegmentMember
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_ShortDurationInsuranceContractAccidentYear2021Member
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: |