XML 58 R48.htm IDEA: XBRL DOCUMENT
v3.23.3

Investments (Allowance on available-for-sale securities with credit impairments and PCD assets activity) (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2023 | Sep. 30, 2022 | Sep. 30, 2023 | Sep. 30, 2022
Allowance for credit losses: |  |  |  |
Balance, beginning of period | $ 22 | $ 5 | $ 1 | $ 18
Additions to the allowance for credit losses: |  |  |  |
Securities for which credit losses were not previously recorded | 5 | 0 | 13 | 0
Available-for-sale securities accounted for as PCD assets | 2 | 0 | 22 | 3
Reductions to the allowance for credit losses: |  |  |  |
Securities sold during the period (realized) | 0 | 0 | 6 | 0
Intent to sell or more likely than not will be required to sell the security before recovery of its amortized cost basis | 0 | 0 | 3 | 0
Write-offs charged against the allowance | 15 | 0 | 15 | 12
Additional increases or (decreases) to the allowance for credit losses on securities that had an allowance recorded in a previous period | 4 | (2) | 6 | (6)
Balance, end of period | 18 | 3 | 18 | 3
Corporate and other bonds |  |  |  |
Allowance for credit losses: |  |  |  |
Balance, beginning of period | 13 | 0 | 0 | 11
Additions to the allowance for credit losses: |  |  |  |
Securities for which credit losses were not previously recorded | 5 | 0 | 6 | 0
Available-for-sale securities accounted for as PCD assets | 2 | 0 | 22 | 0
Reductions to the allowance for credit losses: |  |  |  |
Securities sold during the period (realized) | 0 | 0 | 6 | 0
Intent to sell or more likely than not will be required to sell the security before recovery of its amortized cost basis | 0 | 0 | 3 | 0
Write-offs charged against the allowance | 15 | 0 | 15 | 12
Additional increases or (decreases) to the allowance for credit losses on securities that had an allowance recorded in a previous period | 0 | 0 | 1 | 1
Balance, end of period | 5 | 0 | 5 | 0
Asset-backed |  |  |  |
Allowance for credit losses: |  |  |  |
Balance, beginning of period | 9 | 5 | 1 | 7
Additions to the allowance for credit losses: |  |  |  |
Securities for which credit losses were not previously recorded | 0 | 0 | 7 | 0
Available-for-sale securities accounted for as PCD assets | 0 | 0 | 0 | 3
Reductions to the allowance for credit losses: |  |  |  |
Securities sold during the period (realized) | 0 | 0 | 0 | 0
Intent to sell or more likely than not will be required to sell the security before recovery of its amortized cost basis | 0 | 0 | 0 | 0
Write-offs charged against the allowance | 0 | 0 | 0 | 0
Additional increases or (decreases) to the allowance for credit losses on securities that had an allowance recorded in a previous period | 4 | (2) | 5 | (7)
Balance, end of period | $ 13 | $ 3 | $ 13 | $ 3

X
- Definition Additions To Allowance For Credit Losses + References No definition available. + Details
Name: | cna_AdditionsToAllowanceForCreditLossesAbstract
Namespace Prefix: | cna_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Reductions To Allowance For Credit Losses + References No definition available. + Details
Name: | cna_ReductionsToAllowanceForCreditLossesAbstract
Namespace Prefix: | cna_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of expense for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), for which no credit loss was previously recorded. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 9 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479106/326-30-50-9 + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotPreviouslyRecorded
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of expense (reversal of expense) for allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), not intended to be sold and not more likely than not will be required to sell before recovery of amortized cost basis, with previously recorded allowance. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 9 -Subparagraph (f) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479106/326-30-50-9 + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleAllowanceForCreditLossNotToSellBeforeRecoveryCreditLossPreviouslyRecordedExpenseReversal
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of increase in allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale) and beneficial interest, purchased with credit deterioration. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 9 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479106/326-30-50-9 + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleAllowanceForCreditLossPurchasedWithCreditDeteriorationIncrease
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- 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_DebtSecuritiesAvailableForSaleAllowanceForCreditLossRollForward
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of decrease in allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale) from sale. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 9 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479106/326-30-50-9 + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleAllowanceForCreditLossSecuritiesSold
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of decrease in allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale) from intent to sell or more likely than not will be required to sell before recovery of amortized cost basis. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 9 -Subparagraph (e) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479106/326-30-50-9 + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleAllowanceForCreditLossSellBeforeRecovery
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of writeoff of allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 30 -Name Accounting Standards Codification -Section 50 -Paragraph 9 -Subparagraph (g) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479106/326-30-50-9 + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleAllowanceForCreditLossWriteoff
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount excluding accrued interest, of allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 30 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479130/326-30-45-1 + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostAllowanceForCreditLossExcludingAccruedInterest
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_AssetBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |