XML 148 R134.htm IDEA: XBRL DOCUMENT
v3.22.0.1

Business Segments (Income Statement Information) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Segment Reporting Information [Line Items] |  |  |
Net written premiums | $ 8,405 | $ 8,059 | $ 7,656
Operating revenues |  |  |
Net earned premiums | 8,175 | 7,649 | 7,428
Net investment income | 2,159 | 1,935 | 2,118
Non-insurance warranty revenue | 1,430 | 1,252 | 1,161
Other revenues | 24 | 26 | 31
Total operating revenues | 11,788 | 10,862 | 10,738
Claims, Benefits and Expenses |  |  |
Net incurred claims and benefits | 6,327 | 6,149 | 5,783
Policyholders’ dividends | 22 | 21 | 23
Amortization of deferred acquisition costs | 1,443 | 1,410 | 1,383
Non-insurance warranty expense | 1,328 | 1,159 | 1,082
Other insurance related expenses | 1,062 | 1,028 | 1,038
Other expenses | 242 | 220 | 235
Total claims, benefits and expenses | 10,424 | 9,987 | 9,544
Core income (loss) before income tax | 1,364 | 875 | 1,194
Income tax (expense) benefit on core income (loss) | (258) | (140) | (215)
Core income (loss) | 1,106 | 735 | 979
Net investment gains (losses) | 120 | (54) | 29
Income tax (expense) benefit on net investment gains (losses) | (24) | 9 | (8)
Net investment gains (losses), after tax | 96 | (45) | 21
Net income (loss) | 1,202 | 690 | 1,000
Operating Segments | Specialty |  |  |
Segment Reporting Information [Line Items] |  |  |
Net written premiums | 3,225 | 3,040 | 2,848
Operating revenues |  |  |
Net earned premiums | 3,076 | 2,883 | 2,773
Net investment income | 497 | 449 | 556
Non-insurance warranty revenue | 1,430 | 1,252 | 1,161
Other revenues | 1 | 1 | 1
Total operating revenues | 5,004 | 4,585 | 4,491
Claims, Benefits and Expenses |  |  |
Net incurred claims and benefits | 1,787 | 1,792 | 1,595
Policyholders’ dividends | 3 | 3 | 5
Amortization of deferred acquisition costs | 643 | 621 | 610
Non-insurance warranty expense | 1,328 | 1,159 | 1,082
Other insurance related expenses | 296 | 280 | 292
Other expenses | 47 | 50 | 48
Total claims, benefits and expenses | 4,104 | 3,905 | 3,632
Core income (loss) before income tax | 900 | 680 | 859
Income tax (expense) benefit on core income (loss) | (196) | (145) | (188)
Core income (loss) | 704 | 535 | 671
Operating Segments | Commercial |  |  |
Segment Reporting Information [Line Items] |  |  |
Net written premiums | 3,595 | 3,565 | 3,315
Operating revenues |  |  |
Net earned premiums | 3,552 | 3,323 | 3,162
Net investment income | 624 | 513 | 605
Non-insurance warranty revenue | 0 | 0 | 0
Other revenues | 23 | 25 | 29
Total operating revenues | 4,199 | 3,861 | 3,796
Claims, Benefits and Expenses |  |  |
Net incurred claims and benefits | 2,540 | 2,375 | 2,086
Policyholders’ dividends | 19 | 18 | 18
Amortization of deferred acquisition costs | 594 | 592 | 537
Non-insurance warranty expense | 0 | 0 | 0
Other insurance related expenses | 511 | 506 | 505
Other expenses | 38 | 34 | 32
Total claims, benefits and expenses | 3,702 | 3,525 | 3,178
Core income (loss) before income tax | 497 | 336 | 618
Income tax (expense) benefit on core income (loss) | (103) | (69) | (138)
Core income (loss) | 394 | 267 | 480
Operating Segments | International |  |  |
Segment Reporting Information [Line Items] |  |  |
Net written premiums | 1,101 | 961 | 971
Operating revenues |  |  |
Net earned premiums | 1,057 | 940 | 974
Net investment income | 57 | 58 | 63
Non-insurance warranty revenue | 0 | 0 | 0
Other revenues | 0 | 0 | 0
Total operating revenues | 1,114 | 998 | 1,037
Claims, Benefits and Expenses |  |  |
Net incurred claims and benefits | 652 | 629 | 624
Policyholders’ dividends | 0 | 0 | 0
Amortization of deferred acquisition costs | 206 | 197 | 236
Non-insurance warranty expense | 0 | 0 | 0
Other insurance related expenses | 144 | 136 | 130
Other expenses | (2) | (7) | 8
Total claims, benefits and expenses | 1,000 | 955 | 998
Core income (loss) before income tax | 114 | 43 | 39
Income tax (expense) benefit on core income (loss) | (28) | (5) | (9)
Core income (loss) | 86 | 38 | 30
Operating Segments | Life & Group |  |  |
Segment Reporting Information [Line Items] |  |  |
Net written premiums | 485 | 494 | 523
Operating revenues |  |  |
Net earned premiums | 491 | 504 | 520
Net investment income | 966 | 851 | 820
Non-insurance warranty revenue | 0 | 0 | 0
Other revenues | 0 | 0 | 0
Total operating revenues | 1,457 | 1,355 | 1,340
Claims, Benefits and Expenses |  |  |
Net incurred claims and benefits | 1,239 | 1,286 | 1,416
Policyholders’ dividends | 0 | 0 | 0
Amortization of deferred acquisition costs | 0 | 0 | 0
Non-insurance warranty expense | 0 | 0 | 0
Other insurance related expenses | 103 | 109 | 115
Other expenses | 10 | 7 | 8
Total claims, benefits and expenses | 1,352 | 1,402 | 1,539
Core income (loss) before income tax | 105 | (47) | (199)
Income tax (expense) benefit on core income (loss) | 21 | 56 | 90
Core income (loss) | 126 | 9 | (109)
Operating Segments | Corporate & Other |  |  |
Segment Reporting Information [Line Items] |  |  |
Net written premiums | 0 | 0 | 1
Operating revenues |  |  |
Net earned premiums | 0 | 0 | 1
Net investment income | 15 | 64 | 74
Non-insurance warranty revenue | 0 | 0 | 0
Other revenues | 6 | 5 | 6
Total operating revenues | 21 | 69 | 81
Claims, Benefits and Expenses |  |  |
Net incurred claims and benefits | 109 | 67 | 62
Policyholders’ dividends | 0 | 0 | 0
Amortization of deferred acquisition costs | 0 | 0 | 0
Non-insurance warranty expense | 0 | 0 | 0
Other insurance related expenses | 9 | (2) | (2)
Other expenses | 155 | 141 | 144
Total claims, benefits and expenses | 273 | 206 | 204
Core income (loss) before income tax | (252) | (137) | (123)
Income tax (expense) benefit on core income (loss) | 48 | 23 | 30
Core income (loss) | (204) | (114) | (93)
Eliminations |  |  |
Segment Reporting Information [Line Items] |  |  |
Net written premiums | (1) | (1) | (2)
Operating revenues |  |  |
Net earned premiums | (1) | (1) | (2)
Net investment income | 0 | 0 | 0
Non-insurance warranty revenue | 0 | 0 | 0
Other revenues | (6) | (5) | (5)
Total operating revenues | (7) | (6) | (7)
Claims, Benefits and Expenses |  |  |
Net incurred claims and benefits | 0 | 0 | 0
Policyholders’ dividends | 0 | 0 | 0
Amortization of deferred acquisition costs | 0 | 0 | 0
Non-insurance warranty expense | 0 | 0 | 0
Other insurance related expenses | (1) | (1) | (2)
Other expenses | (6) | (5) | (5)
Total claims, benefits and expenses | (7) | (6) | (7)
Core income (loss) before income tax | 0 | 0 | 0
Income tax (expense) benefit on core income (loss) | 0 | 0 | 0
Core income (loss) | $ 0 | $ 0 | $ 0

X
- Definition Costs From Contract With Customers + References No definition available. + Details
Name: | cna_CostsFromContractWithCustomers
Namespace Prefix: | cna_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Income Tax Expense (Benefit) on Net Realized Investment Gains Losses + References No definition available. + Details
Name: | cna_IncomeTaxExpenseBenefitOnNetRealizedInvestmentGainsLosses
Namespace Prefix: | cna_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Income Tax Expense (Benefit) on Operating Income (Loss) + References No definition available. + Details
Name: | cna_IncomeTaxExpenseBenefitOnOperatingIncomeLoss
Namespace Prefix: | cna_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The income earned from investments in securities and property, equipment and other capital assets. It includes rent from property and equipment, dividends from shares in corporations, and interest from bonds, loans, mortgages, derivatives, commercial paper, bank accounts, certificates of deposits, treasuries, and other financial securities. It also includes realized gains and losses on trading securities. + References No definition available. + Details
Name: | cna_NetInvestmentIncomeAndGainsLossesOnTradingSecurities
Namespace Prefix: | cna_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Net Operating Income (Loss) Attributable to Parent + References No definition available. + Details
Name: | cna_NetOperatingIncomeLossFromContinuingOperationsAttributabletoParent
Namespace Prefix: | cna_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Net Realized Investment Gains (Losses) + References No definition available. + Details
Name: | cna_NetRealizedInvestmentGainsLosses
Namespace Prefix: | cna_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Operating Income (Loss) before Income Tax + References No definition available. + Details
Name: | cna_OperatingIncomeLossFromContinuingOperationsBeforeIncomeTax
Namespace Prefix: | cna_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Operating Revenues + References No definition available. + Details
Name: | cna_OperatingRevenues
Namespace Prefix: | cna_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Other Insurance Related Expenses + References No definition available. + Details
Name: | cna_OtherInsuranceRelatedExpenses
Namespace Prefix: | cna_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The total amount of expense recognized during the period for future policy benefits, claims and claims adjustment costs, and for selling, general and administrative costs. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.5,6,7) -URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263 + Details
Name: | us-gaap_BenefitsLossesAndExpenses
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_BenefitsLossesAndExpensesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of realized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), investment in debt security measured at amortized cost (held-to-maturity) and investment in debt security measured at fair value with change in fair value recognized in net income (trading). + References No definition available. + Details
Name: | us-gaap_DebtSecuritiesRealizedGainLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of amortization expense (reversal of expense) for deferred policy acquisition costs. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 30 -Section 55 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=124504731&loc=d3e11522-158419 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 20 -Section 45 -Paragraph 2 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=6480726&loc=d3e6691-158385 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 65 -Paragraph 2 -Subparagraph (g)(1) -URI http://asc.fasb.org/extlink&oid=124501264&loc=SL117420844-207641 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(7)(a)) -URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 30 -Section 50 -Paragraph 2B -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=124505477&loc=SL117422543-158416 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=35755530&loc=d3e11264-158415 + Details
Name: | us-gaap_DeferredPolicyAcquisitionCostAmortizationExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount after tax of income (loss) from continuing operations attributable to the parent. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 45 -Paragraph 18 -URI http://asc.fasb.org/extlink&oid=123454820&loc=SL4613673-111683 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=124432515&loc=d3e3550-109257 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 45 -Paragraph 60B -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=125511455&loc=SL5780133-109256 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 250 -SubTopic 10 -Section 50 -Paragraph 11 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22694-107794 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 250 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22595-107794 Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.13) -URI http://asc.fasb.org/extlink&oid=123367319&loc=SL114868664-224227 Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3602-108585 Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 250 -SubTopic 10 -Section 50 -Paragraph 11 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22694-107794 Reference 9: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 250 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22583-107794 + Details
Name: | us-gaap_IncomeLossFromContinuingOperations
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of expense classified as other. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.4,6) -URI http://asc.fasb.org/extlink&oid=123367319&loc=SL114868664-224227 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.7) -URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263 + Details
Name: | us-gaap_OtherExpenses
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of revenue and income classified as other. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.4) -URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263 + Details
Name: | us-gaap_OtherIncome
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount, after effects of policies assumed or ceded, of expense related to the provision for policy benefits and costs incurred. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.5) -URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 20 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=99397103&loc=d3e6811-158387 + Details
Name: | us-gaap_PolicyholderBenefitsAndClaimsIncurredNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of expense for dividends to policyholders. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 50 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6483535&loc=d3e16392-158451 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(6)) -URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263 + Details
Name: | us-gaap_PolicyholderDividends
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount, after premiums ceded to other entities and premiums assumed by the entity, of premiums earned. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(1)) -URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 235 -Section S99 -Paragraph 2 -Subparagraph (SX 210.12-17(Column E)) -URI http://asc.fasb.org/extlink&oid=120401096&loc=d3e574992-122915 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04(13)(c)) -URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 + Details
Name: | us-gaap_PremiumsEarnedNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount, after premiums ceded to other entities and premiums assumed by the entity, of premiums written. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 605 -Section 50 -Paragraph 1 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547 + Details
Name: | us-gaap_PremiumsWrittenNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 30 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8906-108599 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 40 -URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e9031-108599 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 41 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e9038-108599 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 32 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 32 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130543-203045 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 22 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8736-108599 Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 22 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8736-108599 Reference 9: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 42 -URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e9054-108599 Reference 10: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 606 -SubTopic 10 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130545-203045 Reference 11: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 924 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 11.L) -URI http://asc.fasb.org/extlink&oid=6472922&loc=d3e499488-122856 + Details
Name: | us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_RevenuesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
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_SegmentReportingInformationLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | srt_ConsolidationItemsAxis=us-gaap_OperatingSegmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

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

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

X
- Details
Name: | srt_ConsolidationItemsAxis=us-gaap_IntersegmentEliminationMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |