Trading Arrangements, by Individual Trading Arrangements, by Individual [Table] Non-investment grade Internal Noninvestment Grade [Member] Weighted average shares outstanding: Weighted Average Number of Shares Outstanding, Diluted [Abstract] Trading Arrangement: Trading Arrangement [Axis] Maximum Maximum [Member] Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] Statistical Measurement [Domain] Statistical Measurement [Domain] Title of 12(b) Security Title of 12(b) Security Carrying Amount Reported Value Measurement [Member] Debt Securities, Available-for-sale [Table] Debt Securities, Available-for-Sale [Table] Document Fiscal Year Focus Document Fiscal Year Focus Expected timing of satisfaction Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period Adjustment to Compensation, Amount Adjustment to Compensation Amount Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Table] Short-Duration Insurance Contracts, Reconciliation of Claims Development to Liability [Table] Financial Instrument [Axis] Financial Instrument [Axis] Income from trading portfolio Income (Loss) From Trading Portfolio [Member] Income (loss) from investments in trading portfolio. Segment Reporting [Abstract] Segment Reporting [Abstract] Common stock Common Stock, Value, Issued Interest Interest Expense, Operating and Nonoperating Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Benefit Plans Retirement Benefits [Text Block] Potential amount of future payments under guarantees Guarantor Obligations, Maximum Exposure, Undiscounted Restatement Determination Date Restatement Determination Date Amortized Cost and Fair Values of Fixed Maturity Securities [Abstract] Debt Securities, Available-for-Sale, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract] Limited partnership investments Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures Expected return on plan assets Defined Benefit Plan, Expected Return (Loss) on Plan Assets Receivables from contracts with customers Contract with Customer, Asset, after Allowance for Credit Loss Other comprehensive income (loss) before reclassifications, tax Other Comprehensive Income (Loss) before Reclassifications, Tax Purchase commitment, remaining minimum amount committed Purchase Commitment, Remaining Minimum Amount Committed Original locked in discount rate Liability for Future Policy Benefit, Weighted-Average Interest Accretion Rate Effect of changes in discount rate Effect of changes in discount rate AOCI, Liability for Future Policy Benefit, Expected Net Premium, before Tax Total insurance reserves Insurance Reserves The aggregate amount of policy reserves (provided for future obligations including unpaid claims and claims adjustment expenses), policy benefits (liability for future policy benefits), unearned premiums and policyholder funds as of the balance sheet date. Amendment Flag Amendment Flag Consolidated Entities [Axis] Consolidated Entities [Axis] Schedule of Impairment Losses (Gains) on Earnings Debt Securities, Available-For-Sale, Impairment Gains (Losses) Recognized In Earnings [Table Text Block] Debt Securities, Available-For-Sale, Impairment Gains (Losses) Recognized In Earnings Debt Securities, Available-for-sale, Measurement Input [Extensible List] Debt Securities, Available-for-Sale, Measurement Input [Extensible Enumeration] Quantitative Information About the Significant Unobservable Inputs [Abstract] Fair Value Measurement Inputs and Valuation Techniques [Abstract] Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Investments in Assets Requiring Future Purchase, Sale or Funding Commitments Investments in Assets Requiring Future Purchase, Sale or Funding Commitments [Member] As part of its overall investment strategy, the Company invests in various assets which require future purchase, sale or funding commitments. These investments are recorded once funded, and the related commitments may include future capital calls from various third-party limited partnerships, signed and accepted mortgage loan applications and obligations related to privately placed debt securities. Net investment income Net investment income Net investment income Net Investment Income Gross Unrealized Losses Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax Asset-backed Total asset-backed Asset-Backed Securities [Member] Balance, January 1, at original locked in discount rate Balance, end of period at original locked in discount rate Liability for Future Policy Benefit, Expected Future Policy Benefit, Original Discount Rate, before Cash Flow and Reinsurance Adjustments to reconcile net income to net cash provided by operating activities, net Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Noncash Item Investments [Domain] Investments [Domain] Other comprehensive income (loss), after tax Other Comprehensive Income (Loss), Net of Tax [Abstract] Liability for Unpaid Claim and Claim Adjustment Expense, Change [Table] Liability for Unpaid Claim and Claim Adjustment Expense, Change [Table] Impairment losses recognized in earnings Debt Securities, Available-For-Sale, Impairment Loss Debt Securities, Available-For-Sale, Impairment Loss Credit spread Measurement Input, Credit Spread [Member] Consolidated Entities [Domain] Consolidated Entities [Domain] Net A&EP claim and allocated claim adjustment expense reserves Liability for Asbestos and Environmental Claims, Net DSCR Less than or Equal to 1.2x, LTV Greater than 65% Debt Service Coverage Ratio Three, Loan-to-value Greater than 65 Percent [Member] Debt service coverage ratio (DSCR) <1.2x and loan-to-value (LTV) ratio greater than 65%. The DSCR compares a property's net operating income to its debt service payments, including principal and interest. The LTV ratio compares the current unpaid principal balance of the loan to the estimated fair value of the underlying property collateralizing the loan. Adjustment to Non-PEO NEO Compensation Footnote Adjustment to Non-PEO NEO Compensation Footnote [Text Block] Transfers into Level 3 Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Transfers Into Level 3 Credit Rating, Fitch [Axis] Credit Rating, Fitch [Axis] Entity Address, State or Province Entity Address, State or Province Total, Gross Unrealized Losses Gross Unrealized Losses Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss Investments: Investment [Abstract] Investment [Abstract] PEO Total Compensation Amount PEO Total Compensation Amount Prior Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year Foreign currency translation Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Shares of common stock (in shares) Weighted Average Number of Shares Outstanding, Basic Retirement Benefits [Abstract] Retirement Benefits [Abstract] Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount DSCR Greater than or Equal to 1.6x, LTV Greater than 65% Debt Service Coverage Ratio One, Loan-to-value Greater than 65 Percent [Member] Debt service coverage ratio (DSCR) >1.6x and loan-to-value (LTV) ratio greater than 65%. The DSCR compares a property's net operating income to its debt service payments, including principal and interest. The LTV ratio compares the current unpaid principal balance of the loan to the estimated fair value of the underlying property collateralizing the loan. Number of reportable segments Number of Reportable Segments Deferred acquisition costs Increase (Decrease) in Deferred Policy Acquisition Costs AA Fitch, AA Rating [Member] Schedule of Activity of Allowance on Available-for-Sale Securities Debt Securities, Available-for-Sale, Allowance for Credit Loss [Table Text Block] Due after five years through ten years Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year 5 Through 10 Operating revenues and other Revenue from Contract with Customer, Excluding Assessed Tax, and Other Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer, excluding non-insurance warranty revenue, and revenue classified as other. 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. Cost or Amortized Cost, Fixed maturities available-for-sale Cost or Amortized Cost Debt Securities, Available-for-Sale, Amortized Cost, Excluding Accrued Interest, before Allowance for Credit Loss Other professional liability and management liability Other Professional Liability and Management Liability Insurance [Member] Contract providing insurance coverage against loss by management and professionals other than medical professionals in course of practice. Entity Address, City or Town Entity Address, City or Town Effect of changes in discount rate AOCI, Liability for Future Policy Benefit, Expected Future Policy Benefit, before Tax Cost or Amortized Cost Debt Securities, Available-for-Sale, Amortized Cost, Fiscal Year Maturity [Abstract] Total consideration Consideration Transferred Under Loss Portfolio Transfer Total consideration transferred to National Indemnity Company ("NICO") under asbestos and environmental claim (A&EP) loss portfolio transfer, including reinsurance premium paid and net book value of billed third party reinsurance receivables transferred. Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Segments: Segment Reporting, Descriptive Information [Abstract] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Award Timing MNPI Disclosure Award Timing MNPI Disclosure [Text Block] Class of Stock [Axis] Class of Stock [Axis] Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Peer Group Total Shareholder Return Amount Peer Group Total Shareholder Return Amount Net incurred claim and claim adjustment expenses: Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract] Level 2 Fair Value, Inputs, Level 2 [Member] Receivable [Domain] Receivable [Domain] Insurance reserves Increase (Decrease) in Insurance Liabilities Total Shareholder Return Vs Peer Group Total Shareholder Return Vs Peer Group [Text Block] Retroactive reinsurance benefit recognized Retroactive Reinsurance Benefit Recognized Amount of retroactive benefit recognized under retroactive reinsurance accounting. Other comprehensive income (loss) Other comprehensive income Other Comprehensive Income (Loss), Net of Tax Non-Rule 10b5-1 Arrangement Terminated Non-Rule 10b5-1 Arrangement Terminated [Flag] Net premiums: earned during period Liability for Future Policy Benefit, Expected Net Premium, Net Premium Collected Debt Securities, Available-for-Sale, Allowance for Credit Loss [Roll Forward] Debt Securities, Available-for-Sale, Allowance for Credit Loss [Roll Forward] Redeemable preferred stock Redeemable Preferred Stock [Member] Net Prior Year Development [Abstract] Insurance Loss Reserves [Abstract] Unrealized gains (losses) on cash flow hedges Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax Schedule of Long-term Debt Instruments [Table] Schedule of Long-Term Debt Instruments [Table] Benefit & expense payments Liability for Future Policy Benefit, Expected Future Policy Benefit, Benefit Payment Additional impairment losses Additional Other-than-temporary Impairment Losses, Investments, Available-for-sale Securities Amount of additional other-than-temporary impairment losses on investments in available-for-sale securities. Investment expenses Investment Income, Investment Expense Investment Income [Table] Investment Income [Table] Accounting Standards Pending Adoption New Accounting Pronouncements, Policy [Policy Text Block] New Accounting Pronouncements or Change in Accounting Principle [Line Items] New Accounting Pronouncements or Change in Accounting Principle [Line Items] Segment Reporting Segment Reporting [Table Text Block] Noncontrolling Interests Noncontrolling Interest [Member] Balance, January 1 Liability for Future Policy Benefit, Expected Net Premium, Before Reinsurance, Before Discount Rate Change Liability for Future Policy Benefit, Expected Net Premium, Before Reinsurance, Before Discount Rate Change CNA CNA Financial CNA Financial CNA Financial Corporation [Member] CNA Financial Corporation (together with its subsidiaries, "CNA") is an insurance holding company. CNA's property and casualty and remaining life and group insurance operations are primarily conducted by Continental Casualty Company ("CCC"), The Continental Insurance Company, Western Surety Company, CNA Insurance Company Limited, Hardy Underwriting Bermuda Limited and its subsidiaries ("Hardy") and CNA Insurance Company (Europe) S.A. Unrealized Gains (Losses) on Cash Flow Hedges Accumulated Gain (Loss), Cash Flow Hedge, Including Noncontrolling Interest [Member] Capital Addition Purchase Commitments Capital Addition Purchase Commitments [Member] Receivables from Contracts with Customers Contract with Customer, Asset, after Allowance for Credit Loss [Abstract] Guarantor Obligations [Line Items] Guarantor Obligations [Line Items] Due after one year through five years Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year One Through Five Other invested assets, primarily mortgage loans, allowance for credit loss Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest 2024 Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year Document Period End Date Document Period End Date Changes in operating assets and liabilities, net: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Increase (Decrease) in Operating Capital [Abstract] Net cash flow used by investing activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation Equity Awards Adjustments, Excluding Value Reported in Compensation Table Equity Awards Adjustments, Excluding Value Reported in the Compensation Table [Member] Face amount Debt Instrument, Face Amount Surety Surety Product Line [Member] Shareholders' Equity Equity [Text Block] Security Exchange Name Security Exchange Name Less treasury stock, at cost (1,668,477 and 0 shares) Treasury Stock, Common, Value Due after ten years Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year 10 Trading securities Increase (Decrease) in Debt Securities, Trading, and Equity Securities, FV-NI Valuation Approach and Technique [Axis] Valuation Approach and Technique [Axis] Liability for future policy benefit, adverse development, expense Liability for Future Policy Benefit, Adverse Development, Expense Other asset-backed Other Asset-Backed Securities [Member] Other Asset-Backed Securities Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Entity Shell Company Entity Shell Company Consolidation Items [Domain] Consolidation Items [Domain] Pension and Postretirement Benefits Accumulated Defined Benefit Plans Adjustment Including Portion Attributable to Noncontrolling Interest [Member] Number of individual operating subsidiaries Number Of Consolidated Operating Subsidiaries Number Of Consolidated Operating Subsidiaries Cumulative impact of changes in discount rates used to measure long duration contracts AOCI, Liability for Future Policy Benefit, Parent [Member] 12 Months or Longer, Estimated Fair Value Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer Statement of Comprehensive Income [Abstract] Statement of Comprehensive Income [Abstract] Workers’ compensation Workers' Compensation Insurance [Member] Name Outstanding Recovery, Individual Name Award Timing, How MNPI Considered Award Timing, How MNPI Considered [Text Block] Document Fiscal Period Focus Document Fiscal Period Focus Peer Group Issuers, Footnote Peer Group Issuers, Footnote [Text Block] Financial Guarantee Financial Guarantee [Member] Total liabilities Liabilities Trading Symbol Trading Symbol DSCR Less than or Equal to 1.2x, LTV Less than 55% Debt Service Coverage Ratio Three, Loan-to-value Less than 55 Percent [Member] Debt service coverage ratio (DSCR) <1.2x and loan-to-value (LTV) ratio less than 55%. The DSCR compares a property's net operating income to its debt service payments, including principal and interest. The LTV ratio compares the current unpaid principal balance of the loan to the estimated fair value of the underlying property collateralizing the loan. Estimated Fair Value, Fixed maturities available-for-sale Estimated Fair Value Fixed maturities available-for-sale Debt Securities, Available-for-Sale, Excluding Accrued Interest Purchases of property, plant and equipment Payments to Acquire Property, Plant, and Equipment Payable to brokers Broker-Dealer, Payable To Other Broker-Dealer, Fair Value Disclosure Broker-Dealer, Payable To Other Broker-Dealer, Fair Value Disclosure Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year Prior Year End Fair Value of Equity Awards Granted in Any Prior Year that Fail to Meet Applicable Vesting Conditions During Covered Year [Member] Pension Adjustments Prior Service Cost Pension Adjustments Prior Service Cost [Member] Company Selected Measure Name Company Selected Measure Name Net Realized Investment Gains (Losses) and Net Change in Unrealized Investment Gains (Losses) Included in OCI Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss) Short-term investments and other Short-term Investments and Other [Member] Investments which are not otherwise included in another category or item that the entity has the intent to sell or dispose of within one year from the date of the balance sheet and investments classified as other. Expected future benefit and expense payments Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance Dividends paid to noncontrolling interests Payments of Ordinary Dividends, Noncontrolling Interest Purchases of fixed maturities Payments to Acquire Debt Securities, Available-for-Sale Purchase Commitment, Excluding Long-Term Commitment [Axis] Purchase Commitment, Excluding Long-Term Commitment [Axis] Gain (losses) on investments, before investment expenses Gains (Losses) on Investments, Before Investment Expenses Amount, before investment expenses, of gains (losses) on investments. Total unrealized gains (losses) on investments OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment and Tax Subsidiary ownership (as a percent) Subsidiary, Ownership Percentage, Parent Pension and Postretirement Benefits Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] Debt Securities, Held-to-maturity, Credit Quality Indicator [Table] Debt Securities, Held-to-Maturity, Credit Quality Indicator [Table] 2026 Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year Equity securities, cost Equity Securities, FV-NI, Cost Asset Class [Domain] Asset Class [Domain] Claim and claim adjustment expense Gross reserves, beginning of year Gross reserves, end of period Liability for Claims and Claims Adjustment Expense Operating Activities: Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract] 4.9% Senior Notes Due 2036 4.9% Senior Notes Due 2036 [Member] 4.9% Senior Notes Due 2036 Compensation Amount Outstanding Recovery Compensation Amount Individual: Individual [Axis] 3.8% Senior Notes Due 2026 3.8% Senior Notes Due 2026 [Member] 3.8% Senior Notes Due 2026 Cumulative impact of changes in discount rates used to measure long duration contracts AOCI, Liability for Future Policy Benefit, Including Noncontrolling Interest [Member] Total weighted average shares outstanding assuming dilution (in shares) Weighted Average Number of Shares Outstanding, Diluted Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Dividends paid (in dollars per share) Common Stock, Dividends, Per Share, Cash Paid Entity Emerging Growth Company Entity Emerging Growth Company Equity Valuation Assumption Difference, Footnote Equity Valuation Assumption Difference, Footnote [Text Block] Loss from catastrophes Loss from Catastrophes Transfers out of Level 3 Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3 Total Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss Underlying Security Market Price Change Underlying Security Market Price Change, Percent Other Other Comprehensive Income, Other, Net of Tax Schedule of Net Investment Income Investment Income [Table Text Block] U.S. Treasury and obligations of government-sponsored enterprises US Treasury Securities [Member] Mortgage Loans Mortgage Receivable [Member] Future Policy Benefits Reserves Long-Duration Insurance Contracts Disclosure [Text Block] Altium Packaging Altium Packaging LLC [Member] Altium Packaging is a packaging solutions provider and manufacturer in North America. Revenue from Contract with Customer [Abstract] Revenue from Contract with Customer [Abstract] Schedule of Reconciliations of Assets and Liabilities Measured at Fair Value on Recurring Basis Using Significant Unobservable Inputs Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Dilutive potential shares of common stock (in shares) Weighted Average Number of Shares Outstanding, Diluted, Adjustment Net unrealized gains (losses) on investments with an allowance for credit losses OCI, Debt Securities, Available-for-Sale, Investments with Allowance for Credit Losses, Unrealized Holding Gain (Loss), After Adjustment, after Tax Amount, after tax and before adjustment, of unrealized holding gain (loss) on investments in debt security with an allowance for credit losses measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). Excludes unrealized gain (loss) on investment in debt security measured at amortized cost (held-to-maturity) from transfer to available-for-sale. DSCR Between 1.2 to 1.6x, LTV Less than 55% Debt Service Coverage Ratio Two, Loan-to-value Less than 55 Percent [Member] Debt service coverage ratio (DSCR) between 1.2x and 1.6x and loan-to-value (LTV) ratio less than 55%. The DSCR compares a property's net operating income to its debt service payments, including principal and interest. The LTV ratio compares the current unpaid principal balance of the loan to the estimated fair value of the underlying property collateralizing the loan. Award Timing Predetermined Award Timing Predetermined [Flag] Earned premiums Liability for Future Policy Benefit, Gross Premium Income DSCR Less than or Equal to 1.2x, LTV 55% to 65% Debt Service Coverage Ratio Three, Loan-to-value 55 to 65 Percent [Member] Debt service coverage ratio (DSCR) <1.2x and loan-to-value (LTV) ratio between 55% and 65%. The DSCR compares a property's net operating income to its debt service payments, including principal and interest. The LTV ratio compares the current unpaid principal balance of the loan to the estimated fair value of the underlying property collateralizing the loan. Common Stock Held in Treasury Treasury Stock, Common [Member] Debt Securities, Available-for-sale [Line Items] Debt Securities, Available-for-Sale [Line Items] Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Stock-based compensation APIC, Share-Based Payment Arrangement, Increase for Cost Recognition Insurance claims and policyholders’ benefits (re-measurement loss of $25, $15, $44 and $23) Insurance claims and policyholders’ benefits Policyholder Benefits and Claims Incurred, Net Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items] Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items] Level 1 Fair Value, Inputs, Level 1 [Member] Net reserves, beginning of year Net reserves, end of period Liability for Unpaid Claims and Claims Adjustment Expense, Net Net Unrealized Gains (Losses) on Other Investments AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-Sale, Including Noncontrolling Interest [Member] All Executive Categories All Executive Categories [Member] Valuation Approach and Technique [Domain] Valuation Approach and Technique [Domain] Pension Adjustments Service Cost Pension Adjustments Service Cost [Member] Residential mortgage-backed Residential Mortgage-Backed Securities [Member] General liability General Liability [Member] Preferred stock, par value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Long-term debt Long-Term Debt, Fair Value Schedule of Net Periodic (Benefit) Cost Components Schedule of Net Benefit Costs [Table Text Block] External Credit Rating, Fitch [Domain] External Credit Rating, Fitch [Domain] Antidilutive Securities [Axis] Antidilutive Securities [Axis] Schedule of Net Prior Year Loss Reserve Development in Property and Casualty Operations Schedule of Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Table Text Block] DSCR Between 1.2 to 1.6x, LTV 55% to 65% Debt Service Coverage Ratio Two, Loan-to-value 55 to 65 Percent [Member] Debt service coverage ratio (DSCR) between 1.2x and 1.6x and loan-to-value (LTV) ratio between 55% and 65%. The DSCR compares a property's net operating income to its debt service payments, including principal and interest. The LTV ratio compares the current unpaid principal balance of the loan to the estimated fair value of the underlying property collateralizing the loan. Settlements Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward] AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward] Net payments attributable to: Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract] Guarantor Obligations, Nature [Axis] Guarantor Obligations, Nature [Axis] Due in one year or less Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, Year One Cost or Amortized Cost, Fixed maturities trading Debt Securities, Trading, Amortized Cost Aggregate income (loss) recognized due to the change in fair value of equity and trading portfolio securities held Trading Securities, Change in Unrealized Holding Gain (Loss), Net Investment Income Recognized Trading Securities, Change in Unrealized Holding Gain (Loss), Net Investment Income Recognized Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Debt Disclosure [Abstract] Debt Disclosure [Abstract] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Short-term debt Long-Term Debt and Lease Obligation, Current Segments Segment Reporting [Text Block] Investments Investment in Debt and Equity Securities and Other Trading Assets [Text Block] Proceeds from maturities of fixed maturities Proceeds from Maturities, Prepayments and Calls of Debt Securities, Available-for-Sale Minimum Minimum [Member] Investment Type [Axis] Investment Type [Axis] Dividends paid Payments of Ordinary Dividends, Common Stock Expiration Date Trading Arrangement Expiration Date Schedule of Disaggregation of Revenue Disaggregation of Revenue [Table Text Block] Cumulative Effect, Period of Adoption, Adjustment Cumulative Effect, Period of Adoption, Adjustment [Member] Effect of foreign exchange rate on cash Effect of Exchange Rate on Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Adjusted balance, January 1 Liability for Future Policy Benefit, Expected Future Benefit, Original Discount Rate, before Reinsurance, after Cash Flow Change Non-Rule 10b5-1 Arrangement Adopted Non-Rule 10b5-1 Arrangement Adopted [Flag] Total equity Balance at beginning of period Balance at end of period Equity, Including Portion Attributable to Noncontrolling Interest Limited partnership investments Partnership Interest [Member] Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table Aggregate Grant Date Fair Value of Equity Award Amounts Reported in Summary Compensation Table [Member] Other liabilities Other Liabilities Business Combination [Line Items] Business Combination [Line Items] Trial court, plaintiff award, plus pre-judgement interest Trial Court, Plaintiff Award, Plus Pre-Judgement Interest Trial Court, Plaintiff Award, Plus Pre-Judgement Interest Net periodic benefit Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Aggregate Pension Adjustments Service Cost Aggregate Pension Adjustments Service Cost [Member] Common stock, shares authorized (in shares) Common Stock, Shares Authorized Proceeds from sales of limited partnership investments Proceeds from Limited Partnership Investments Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] A&EP Reserves Asbestos And Environmental Pollution Reserves [Member] Asbestos and environmental pollution reserves. Trial court, plaintiff award Trial Court, Plaintiff Award Trial Court, Plaintiff Award Due after ten years Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year 10 Exercise Price Award Exercise Price Investing Activities: Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract] Segment Reporting [Line Items] Segment Reporting [Line Items] Document Quarterly Report Document Quarterly Report Debt Securities, Available-for-sale, Valuation Technique [Extensible List] Debt Securities, Available-for-Sale, Valuation Technique [Extensible Enumeration] Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested Year-over-Year Change in Fair Value of Equity Awards Granted in Prior Years That are Outstanding and Unvested [Member] Segments [Domain] Segments [Domain] States, municipalities and political subdivisions US States and Political Subdivisions Debt Securities [Member] Proceeds from sales of fixed maturities Proceeds from Sale of Debt Securities, Available-for-Sale Receivables Accounts Receivable, after Allowance for Credit Loss Debt Debt Disclosure [Text Block] Prior year events Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years Pretax (favorable) unfavorable development Total pretax unfavorable development Liability for Unpaid Claims and Claims Adjustment Expense, Period Increase (Decrease) Receivables Receivables, Fair Value Disclosure Awards Close in Time to MNPI Disclosures, Table Awards Close in Time to MNPI Disclosures [Table Text Block] Credit Quality Information [Abstract] Credit Quality Information [Abstract] Business Combination [Table] Business Combination [Table] Equity Component [Domain] Equity Component [Domain] Fixed maturities, amortized cost Cost or Amortized Cost, Total fixed maturity securities Debt Securities, Amortized Cost Debt Securities, Amortized Cost Deferred acquisition costs of insurance subsidiaries Deferred Policy Acquisition Cost PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount Measurement Input Type [Domain] Measurement Input Type [Domain] Net Realized Investment Gains (Losses) and Net Change in Unrealized Investment Gains (Losses) Included in Net Income Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings Business Combination, Asset Acquisition, Transaction between Entities under Common Control, and Joint Venture Formation [Abstract] Other invested assets, primarily mortgage loans Loans Receivable, Fair Value Disclosure Expenses: Benefits, Losses and Expenses [Abstract] Adoption Date Trading Arrangement Adoption Date Lodging and related services – Loews Hotels & Co Lodging and Related Services [Member] Loews Hotels & Co provides lodging and related goods and services as well as management and marketing services. Lodging and related revenues are recognized as the guest takes possession of the goods or receives the services. Management and marketing services revenues are recognized as the services are provided and billed on a monthly basis. In addition, Loews Hotels & Co recognizes revenue for the reimbursement of payroll and other expenses as they are incurred on behalf of the owners of joint venture and managed hotel properties. Deferred Revenue Contract with Customer, Liability [Abstract] Interest rate (as a percent) Debt Instrument, Interest Rate, Stated Percentage Total shareholders’ equity Equity, Attributable to Parent Payable to brokers Broker-Dealer, Payable to Other Broker-Dealer and Clearing Organization Settlements Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement Net Unrealized Gains (Losses) on Investments with an Allowance for Credit Losses AOCI, Gain (Loss), Debt Securities, Available-for-Sale, with Allowance for Credit Loss, Including Noncontrolling Interest [Member] Equity securities, cost of $1,309 and $1,201 Equity Securities, FV-NI, Current Assets: Assets [Abstract] Title Trading Arrangement, Individual Title Forgone Recovery due to Disqualification of Tax Benefits, Amount Forgone Recovery due to Disqualification of Tax Benefits, Amount Other invested assets, primarily mortgage loans, less allowance for credit loss of $15 and $15 Other Investments Accounting Policies [Abstract] Accounting Policies [Abstract] Restatement does not require Recovery Restatement Does Not Require Recovery [Text Block] Insider Trading Policies and Procedures [Line Items] Non-insurance warranty – CNA Financial Non-Insurance Warranty [Member] CNA Financial Corporation's non-insurance warranty revenues are primarily generated from separately-priced service contracts that provide mechanical breakdown and other coverages to vehicle or consumer goods owners, which generally provide coverage from one month to ten years. Other revenues Other Operating Income Other, net Proceeds from (Payment for) Other Financing Activity Insider Trading Policies and Procedures Adopted Insider Trading Policies and Procedures Adopted [Flag] Adjusted Balance Cumulative Effect, Period of Adoption, Adjusted Balance [Member] Current year events Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year Total net incurred Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims Net unrealized gains (losses) on other investments OCI, Debt Securities, Available-for-Sale, Other Investments, Unrealized Holding Gain (Loss), After Adjustment, after Tax Amount, after tax and before adjustment, of unrealized holding gain (loss) on other investments in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). Excludes unrealized gain (loss) on investment in debt security measured at amortized cost (held-to-maturity) from transfer to available-for-sale. Principal payments on debt Repayments of Debt Business Combination [Domain] Business Combination [Domain] Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Compensation Actually Paid vs. Net Income Compensation Actually Paid vs. Net Income [Text Block] Cumulative amounts ceded under loss portfolio transfer Cumulative Amounts Ceded Under Loss Portfolio Transfer Cumulative amounts ceded to National Indemnity Company ("NICO") under asbestos and environmental claim (A&EP) loss portfolio transfer. Shares excluded from diluted EPS calculation (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Entity Central Index Key Entity Central Index Key Weighted Average Weighted Average [Member] All Adjustments to Compensation All Adjustments to Compensation [Member] Guarantor Obligation [Table] Guarantor Obligation [Table] Balance, January 1 Liability for Future Policy Benefit, Expected Future Policy Benefit, Before Reinsurance, Before Discount Rate Change Liability for Future Policy Benefit, Expected Future Policy Benefit, Before Reinsurance, Before Discount Rate Change Business Combination [Axis] Business Combination [Axis] Equity [Abstract] Equity [Abstract] Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year Dividends or Other Earnings Paid on Equity Awards not Otherwise Reflected in Total Compensation for Covered Year [Member] Net cash flow provided by operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation Future policy benefits Net LFPB Liability for Future Policy Benefit, before Reinsurance Amounts attributable to noncontrolling interests Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest Legal Proceedings Legal Matters and Contingencies [Text Block] Increase (decrease) in provision for insured events of prior years Prior Year Claims and Claims Adjustment Expense Other Stockholders' Equity, Other Other comprehensive income (loss) before reclassifications, after tax Other Comprehensive Income (Loss), before Reclassifications, Net of Tax Income Statement [Abstract] Income Statement [Abstract] Document Transition Report Document Transition Report Liability for future policy benefit, weighted-average duration Liability for Future Policy Benefit, Weighted-Average Duration Ownership [Axis] Ownership [Axis] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Investment losses Investment gains (losses) Investment losses Gain (Loss) on Investments Investment, Name [Axis] Investment, Name [Axis] Fixed maturity securities Total fixed maturity securities Fixed Maturities [Member] Stock Appreciation Rights (SARs) Stock Appreciation Rights (SARs) [Member] Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] Other Commitments [Domain] Other Commitments [Domain] City Area Code City Area Code Reinsurance premium paid to NICO under A&EP loss portfolio transfer Reinsurance Premium Amount of reinsurance premium paid to National Indemnity Company ("NICO") under asbestos and environmental claim (A&EP) loss portfolio transfer. Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] All Individuals All Individuals [Member] Corporate Corporate Segment [Member] Name Forgone Recovery, Individual Name Reconciliations for All Assets and Liabilities [Roll Forward] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Schedule of Investment Gains (Losses) Realized Gain (Loss) on Investments [Table Text Block] Non-GAAP Measure Description Non-GAAP Measure Description [Text Block] Statement [Line Items] Statement [Line Items] Total assets Total assets Assets Defined Benefit Plan [Table] Defined Benefit Plan [Table] DSCR Greater than or Equal to 1.6x, LTV Less than 55% Debt Service Coverage Ratio One, Loan-to-value Less than 55 Percent [Member] Debt service coverage ratio (DSCR) >1.6x and loan-to-value (LTV) ratio less than 55%. The DSCR compares a property's net operating income to its debt service payments, including principal and interest. The LTV ratio compares the current unpaid principal balance of the loan to the estimated fair value of the underlying property collateralizing the loan. Amortization of unrecognized prior service cost Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Operating Segments Operating Segments [Member] Securities disposed during the period (realized) Debt Securities, Available-for-Sale, Excluding Accrued Interest, Allowance for Credit Loss, Sold Gross Unrealized Gains Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax Liabilities assumed Business Combination, Recognized Liability Assumed, Liability Change in short-term investments Payments for (Proceeds from) Short-Term Investments Other assets Increase (Decrease) in Other Operating Assets PEO PEO [Member] Unrecognized deferred retroactive reinsurance benefit Unrecognized Deferred Retroactive Reinsurance Benefit Amount of unrecognized benefit related to loss portfolio transfer to National Indemnity Company ("NICO") under retroactive reinsurance accounting. Measurement Basis [Axis] Measurement Basis [Axis] Short-term investments Marketable Securities, Current Goodwill Goodwill Retirement Plan Type [Axis] Retirement Plan Type [Axis] Commitments to sell investments Commitments to Sell Investments Minimum amount of other commitment in which the entity has agreed to sell investments related to various third-party limited partnerships, signed and accepted mortgage loan applications and obligations related to privately placed debt securities. Forgone Recovery due to Violation of Home Country Law, Amount Forgone Recovery due to Violation of Home Country Law, Amount Fixed maturities trading Fixed Maturities Trading [Member] Trading security investments measured at fair value that provides a return in the form of fixed periodic payments and eventual return of principal at maturity. Fair Value Measurement Inputs and Valuation Techniques [Line Items] Fair Value Measurement Inputs and Valuation Techniques [Line Items] Total investments Investments Revenue recognized Contract with Customer, Liability, Revenue Recognized Due in one year or less Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, Year One Other property and casualty operations Property And Casualty Operations, Other [Member] Property And Casualty Operations, Other Retained Earnings Retained Earnings [Member] Net Unrealized Gains (Losses) on Other Investments AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-Sale, Parent [Member] Erroneously Awarded Compensation Recovery Erroneously Awarded Compensation Recovery [Table] Schedule of Significant Unobservable Inputs Fair Value Measurement Inputs and Valuation Techniques [Table Text Block] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Award Timing Disclosures [Line Items] Disaggregation of Revenues Disaggregation of Revenue [Abstract] Foreign Currency Translation Accumulated Foreign Currency Adjustment Attributable to Parent [Member] Corporate and other bonds Corporate bonds and other Corporate Debt Securities [Member] Diluted net income per share (in dollars per share) Earnings Per Share, Diluted Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Table] Foreign currency translation adjustment and other Liability for Unpaid Claims and Claims Adjustment Expense, Foreign Currency Translation Gain (Loss) Entity Current Reporting Status Entity Current Reporting Status Net cash flow used by financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation Total Shareholder Return Amount Total Shareholder Return Amount Non-insurance warranty revenue Non-Insurance Warranty Revenue Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer from non-insurance warranty revenue. 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. Impact of changes in discount rates used to measure long-duration contract liabilities OCI, Liability for Future Policy Benefit, Gain (Loss), after Reclassification Adjustment and Tax Ownership [Domain] Ownership [Domain] 2023 Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year Assets acquired Business Combination, Recognized Asset Acquired, Asset Shareholders' equity before treasury stock, total Stockholders' Equity before Treasury Stock Total revenues from contracts with customers Revenue from Contract with Customer, Excluding Assessed Tax Reclassification of losses from accumulated other comprehensive loss, tax Reclassification from AOCI, Current Period, Tax Financing Activities: Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract] Property, plant and equipment Property, Plant, and Equipment, after Accumulated Depreciation, Depletion, and Amortization Interest cost Defined Benefit Plan, Interest Cost Net Investment Income [Line Items] Net Investment Income [Line Items] Financial Instruments [Domain] Financial Instruments [Domain] Assets: Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] 2022 Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year Operating revenues and other Operating revenues and other Other Income Additional increases to the allowance for credit losses on securities that had an allowance recorded in a previous period Debt Securities, Available-for-Sale, Excluding Accrued Interest, Allowance for Credit Loss, Not to Sell before Recovery, Credit Loss, Previously Recorded, Expense (Reversal) Equity Awards Adjustments, Footnote Equity Awards Adjustments, Footnote [Text Block] Underlying Securities Award Underlying Securities Amount Amounts attributable to noncontrolling interests Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Estimated Fair Value Estimate of Fair Value Measurement [Member] Revenue from Contracts with Customers Revenue from Contract with Customer [Text Block] Securities for which credit losses were not previously recorded Debt Securities, Available-for-Sale, Excluding Accrued Interest, Allowance for Credit Loss, Not Previously Recorded Balance, January 1, at original locked in discount rate Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Cash Flow and Reinsurance Sales Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales Cash Cash Other, net Payment for (Proceeds from) Other Investing Activity Available-for-sale Fixed Maturities Fixed maturities available-for-sale Fixed Maturities Available-for-Sale [Member] Available-for-sale security investments measured at fair value that provides a return in the form of fixed periodic payments and eventual return of principal at maturity. Expected future gross premiums Liability for Future Policy Benefit, Expected Future Gross Premium, Undiscounted, before Reinsurance Segment Reporting [Table] Segment Reporting [Table] Loews Hotels & Co Loews Hotels Holding Corporation [Member] Loews Hotels Holding Corporation (together with its subsidiaries, "Loews Hotels & Co") operates a chain of 26 hotels. 11 of these hotels are owned by Loews Hotels & Co, 10 are owned by joint ventures in which Loews Hotels & Co has equity interests and five are managed for unaffiliated owners. Commitments and Contingencies [Abstract] Guarantees [Abstract] Non-insurance warranty expense Non-insurance Warranty Expense Amount of expenses recognized from non-insurance warranty. Debt-to-Value [Domain] Debt-to-Value [Domain] Fixed maturity securities available-for-sale: Other-than-temporary Impairment Loss, Debt Securities, Available-for-Sale [Abstract] Schedule of Amortized Cost and Fair Values of Fixed Maturity Securities Schedule of Available-for-Sale Securities Reconciliation [Table Text Block] Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] All Trading Arrangements All Trading Arrangements [Member] Less than 12 Months, Estimated Fair Value Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months Other Performance Measure, Amount Other Performance Measure, Amount Award Timing MNPI Considered Award Timing MNPI Considered [Flag] Remaining performance obligations Revenue, Remaining Performance Obligation, Amount Current Fiscal Year End Date Current Fiscal Year End Date Upper-medium grade fixed income instrument discount rate Liability for Future Policy Benefit, Current Weighted-Average Discount Rate Issuance of debt Proceeds from Issuance of Debt Schedule of Amortized Cost Basis of Mortgage Loans for Each Credit Quality Indicator by Year of Origination Debt Securities, Held-to-Maturity, Credit Quality Indicator [Table Text Block] Non-PEO NEO Average Total Compensation Amount Non-PEO NEO Average Total Compensation Amount Losses recognized on mortgage loans due to changes in expected credit losses Financing Receivable, Excluding Accrued Interest, Credit Loss Expense (Reversal) Acquisitions Business Combination [Text Block] Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items] Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items] Number of shares of common stock issued to settle stock-based compensation awards Shares Issued, Shares, Share-Based Payment Arrangement, before Forfeiture Cumulative Effect, Period of Adoption [Domain] Cumulative Effect, Period of Adoption [Domain] Re-measurement impact of insurance claims and policyholders’ benefits Insurance Claims And Policyholders Benefits, Including Policyholders' Dividends, Remeasurement Impact Insurance Claims And Policyholders Benefits, Including Policyholders' Dividends, Remeasurement Impact Foreign government Debt Security, Government, Non-US [Member] Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year Change in Fair Value as of Vesting Date of Prior Year Equity Awards Vested in Covered Year [Member] Entity File Number Entity File Number Rule 10b5-1 Arrangement Adopted Rule 10b5-1 Arrangement Adopted [Flag] Service cost Defined Benefit Plan, Service Cost Schedule of Available-for-sale Fixed Maturity Securities by Contractual Maturity Investments Classified by Contractual Maturity Date [Table Text Block] Equity securities Equity securities Equity Securities [Member] Schedule of Reconciliation of Claim and Claim Adjustment Expense Reserves Schedule of Liability for Unpaid Claims and Claims Adjustment Expense [Table Text Block] Ceded A&EP claim and allocated claim adjustment expense reserves under existing third party reinsurance contracts transferred to NICO under A&EP loss portfolio transfer Liability for Asbestos and Environmental Claims, Ceded under Existing Third Party Reinsurance Contracts Amount of asbestos and environmental ceded claim and allocated claim adjustment expense reserves under existing third party reinsurance contracts. Measurement input Debt Securities, Available-for-Sale, Measurement Input Recovery of Erroneously Awarded Compensation Disclosure [Line Items] Common stock, shares issued (in shares) Common Stock, Shares, Issued Measure: Measure [Axis] Balance at beginning of period Balance at ending of period Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value Treasury stock, shares (in shares) Treasury Stock, Common, Shares Insurance premiums Premiums Earned, Net Assets and Liabilities Measured at Fair Value [Abstract] Fair Value, Net Asset (Liability) [Abstract] 12 Months or Longer, Gross Unrealized Losses Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss Operating expenses Other Cost and Expense, Operating Equity Components [Axis] Equity Components [Axis] Receivables Increase (Decrease) in Accounts Receivable Effect of changes in cash flow assumptions Liability for Future Policy Benefit, Expected Net Premium, Cumulative Increase (Decrease) from Cash Flow Change Product and Service [Domain] Product and Service [Domain] Cumulative Effect, Period of Adoption [Axis] Cumulative Effect, Period of Adoption [Axis] Deferred non-insurance warranty acquisition expenses Capitalized Contract Cost, Net Depreciation and amortization Depreciation and Amortization Expense, Adjusted Depreciation and Amortization Expense, Adjusted Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Entity Interactive Data Current Entity Interactive Data Current Amounts attributable to noncontrolling interests Net Income (Loss) Attributable to Noncontrolling Interest Deferred income taxes Deferred Income Tax Liabilities, Net Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] Due after one year through five years Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year One Through Five Estimated Fair Value Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Fair Value [Abstract] Net reinsurance receivables transferred to NICO under A&EP loss portfolio transfer Billed Third Party Reinsurance Receivables, Net Book Value Net book value of billed third party reinsurance receivables transferred to National Indemnity Company ("NICO") under asbestos and environmental claim (A&EP) loss portfolio transfer. Entity Small Business Entity Small Business Total comprehensive income attributable to Loews Corporation Comprehensive Income (Loss), Net of Tax, Attributable to Parent Unearned premiums Unearned Premiums Termination Date Trading Arrangement Termination Date Other Commitments [Axis] Other Commitments [Axis] Fair Value Disclosure of Asset and Liability Not Measured at Fair Value [Table] Fair Value Disclosure of Asset and Liability Not Measured at Fair Value [Table] Fair Value, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Compensation Actually Paid vs. Total Shareholder Return Compensation Actually Paid vs. Total Shareholder Return [Text Block] Pension and postretirement benefits Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax MNPI Disclosure Timed for Compensation Value MNPI Disclosure Timed for Compensation Value [Flag] Provision for insured events of current year Current Year Claims and Claims Adjustment Expense U.S. Government, Government agencies and Government-sponsored enterprises US Government-sponsored Enterprises Debt Securities [Member] Interest accrual Liability for Future Policy Benefit, Expected Future Policy Benefit, Interest Expense Document Type Document Type Acquisitions Payments to Acquire Businesses, Net of Cash Acquired Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Purchase Commitment, Excluding Long-Term Commitment [Domain] Purchase Commitment, Excluding Long-Term Commitment [Domain] Fair Value as of Grant Date Award Grant Date Fair Value Beginning balance Ending balance Debt Securities, Available-for-Sale, Allowance for Credit Loss, Excluding Accrued Interest Schedule of Available-for-sale Fixed Maturity Securities in Gross Unrealized Loss Position Debt Securities, Available-for-Sale, Unrealized Loss Position, Fair Value [Table Text Block] Other insurance operations Insurance, Other [Member] Pay vs Performance Disclosure, Table Pay vs Performance [Table Text Block] Arrangement Duration Trading Arrangement Duration Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Local Phone Number Local Phone Number Other Postretirement Benefits Other Postretirement Benefits Plan [Member] Consolidation Items [Axis] Consolidation Items [Axis] Entity Address, Postal Zip Code Entity Address, Postal Zip Code Entity Registrant Name Entity Registrant Name Liability future policy benefit, losses recognized in prior period Liability Future Policy Benefit, Losses Recognized In Prior Period And Reversed Through Net Income Liability Future Policy Benefit, Losses Recognized In Prior Period And Reversed Through Net Income DSCR Between 1.2 to 1.6x, LTV Greater than 65% Debt Service Coverage Ratio Two, Loan-to-value Greater than 65 Percent [Member] Debt service coverage ratio (DSCR) between 1.2x and 1.6x and loan-to-value (LTV) ratio greater than 65%. The DSCR compares a property's net operating income to its debt service payments, including principal and interest. The LTV ratio compares the current unpaid principal balance of the loan to the estimated fair value of the underlying property collateralizing the loan. Less than 12 Months, Gross Unrealized Losses Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss Income before income tax Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Insider Trading Policies and Procedures Not Adopted Insider Trading Policies and Procedures Not Adopted [Text Block] Schedule of Financial Assets and Liabilities not Measured at Fair Value Fair Value Disclosure of Asset and Liability Not Measured at Fair Value [Table Text Block] Commitments and contingent liabilities Commitments and Contingencies Total Revenues Antidilutive Securities, Name [Domain] Antidilutive Securities, Name [Domain] Changed Peer Group, Footnote Changed Peer Group, Footnote [Text Block] Equity method income Equity method (income) loss Income (Loss) from Equity Method Investments Operating expenses and other Operating expenses and other Operating Expenses And Other Operating Expenses And Other Accounting Standards Update and Change in Accounting Principle [Table] Accounting Standards Update and Change in Accounting Principle [Table] Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount Executive Category: Executive Category [Axis] Receivable Type [Axis] Receivable Type [Axis] Short-term and other Short-Term Investments And Other, Fair Value Disclosure Short-Term Investments And Other, Fair Value Disclosure Operating Expenses and Other: Operating Costs and Expenses [Abstract] Liabilities and Equity: Liabilities and Equity [Abstract] Other Commitments [Table] Other Commitments [Table] Gross gains Investment Gains, Gross Investment Gains, Gross Transportation and storage of natural gas and NGLs and ethane supply and transportation services – Boardwalk Pipelines Transportation and Storage of Natural Gas and NGLs and Ethane Supply and Transportation Services [Member] Boardwalk Pipelines primarily earns revenues by providing transportation and storage services for natural gas and natural gas liquids and hydrocarbons (referred to together as "NGLs") on a firm and interruptible basis and provides interruptible natural gas parking and lending services. Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] All Award Types Award Type [Domain] Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount Balance, June 30 Liability for Future Policy Benefit, Expected Net Premium, before Reinsurance, after Discount Rate Change Fair Value Fair Value Disclosures [Text Block] Boardwalk Pipelines Boardwalk Pipelines Boardwalk Pipeline Partners, LP [Member] Boardwalk Pipeline Partners, LP (together with its subsidiaries, "Boardwalk Pipelines") is engaged in the business of natural gas and natural gas liquids and hydrocarbons (herein referred to together as "NGLs") transportation and storage. Level 3 Fair Value, Inputs, Level 3 [Member] Schedule of Liability for Future Policy Benefit Liability for Future Policy Benefit, Activity [Table Text Block] Purchases of treasury stock (in shares) Treasury Stock, Shares, Acquired Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] PEO Name PEO Name Total net payments Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid Available-for-sale securities accounted for as PCD assets Debt Securities, Available-for-Sale, Excluding Accrued Interest, Purchased with Credit Deterioration, Allowance for Credit Loss at Acquisition Date Deferred revenue Contract with Customer, Liability Unrealized Gains (Losses) on Cash Flow Hedges Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member] Debt Securities, Available-for-sale, Allowance for Credit Loss [Line Items] Debt Securities, Available-for-Sale, Allowance for Credit Loss [Line Items] Interest accrual Liability for Future Policy Benefit, Expected Net Premium, Interest Income Liabilities: Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract] Other Segment Reporting, Other Segment Item, Amount Other assets Other Assets Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] Entity Tax Identification Number Entity Tax Identification Number Aggregate limit under A&EP loss portfolio transfer Liability for Asbestos and Environmental Claims, Net, Aggregate Limit Aggregate limit of net asbestos and environmental claim and allocated claim adjustment expense reserves ceded to National Indemnity Company ("NICO") under a retroactive reinsurance agreement. Other Commitments [Line Items] Other Commitments [Line Items] 6.0% Senior Notes Due 2026 6.0% Senior Notes Due 2026 [Member] 6.0% Senior Notes Due 2026 Purchases of Loews Corporation treasury stock Purchases of treasury stock Treasury Stock, Value, Acquired, Cost Method Cash, beginning of period Cash, end of period Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Fixed maturities, amortized cost of $45,697 and $45,250, less allowance for credit loss of $63 and $69 Total fixed maturities Debt Securities Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Aggregate Erroneous Compensation Not Yet Determined Aggregate Erroneous Compensation Not Yet Determined [Text Block] Schedule of Amount Reclassification From AOCI Reclassification out of Accumulated Other Comprehensive Income [Table Text Block] Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] Non-NEOs Non-NEOs [Member] Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year Vesting Date Fair Value of Equity Awards Granted and Vested in Covered Year [Member] Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items] Short-Duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items] AAA Fitch, AAA Rating [Member] Comprehensive income Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Debt Instrument [Axis] Debt Instrument [Axis] Equity method investment, ownership percentage (as a percent) Equity Method Investment, Ownership Percentage Dividends paid Dividends, Cash Purchases of subsidiary stock from noncontrolling interests Payments for Repurchase of Redeemable Noncontrolling Interest Investment, Name [Domain] Investment, Name [Domain] Due after five years through ten years Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year 5 Through 10 Basic net income per share (in dollars per share) Earnings Per Share, Basic Measurement Input Type [Axis] Measurement Input Type [Axis] Deferred non-insurance warranty revenue Deferred Revenue Purchases of Loews Corporation treasury stock Payments for Repurchase of Common Stock Statistical Measurement [Axis] Statistical Measurement [Axis] Insider Trading Arrangements [Line Items] Short-term debt Short-Term Debt, Fair Value Nonredeemable Preferred Stock Nonredeemable Preferred Stock [Member] Award Type Award Type [Axis] Effect of actual variances from expected experience Liability for Future Policy Benefit, Expected Future Policy Benefit, Cumulative Increase (Decrease) of Actual Variance from Expected Experience Present value of future net premiums Liability for Future Policy Benefit, Expected Net Premium [Roll Forward] Fixed maturity securities: Debt and Equity Securities, Gain (Loss) [Abstract] Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] Retained earnings Retained Earnings (Accumulated Deficit) Amortization of discount Liability for Unpaid Claims and Claims Adjustment Expense Incurred Claims, Amortization of Discount Amortization of discount related to claim and claim adjustment expenses. Product and Service [Axis] Product and Service [Axis] Equity securities Equity Securities, FV-NI Amortization of deferred acquisition costs Deferred Policy Acquisition Costs, Amortization Expense Fixed maturities, allowance for credit loss Allowance for Credit Losses Debt Securities, Available-for-Sale, Amortized Cost, Allowance for Credit Loss, Excluding Accrued Interest, Current BBB Fitch, BBB Rating [Member] Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table Aggregate Change in Present Value of Accumulated Benefit for All Pension Plans Reported in Summary Compensation Table [Member] Awards Close in Time to MNPI Disclosures Awards Close in Time to MNPI Disclosures [Table] Pension Benefits Pension Plan [Member] Common Stock Common Stock [Member] Fair Value Measurement [Domain] Fair Value Measurement [Domain] Derivative assets acquired Business Combination, Recognized Asset Acquired, Derivative Assets Business Combination, Recognized Asset Acquired, Derivative Assets Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] Cover [Abstract] Cover [Abstract] Insurance reserves: Insurance [Abstract] Unrealized Gains (Losses) Recognized in Other Comprehensive Income (Loss) on Level 3 Assets and Liabilities Held at June 30 Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), OCI Fair Value Measurement Inputs and Valuation Techniques [Table] Fair Value Measurement Inputs and Valuation Techniques [Table] Effect of changes in cash flow assumptions Liability for Future Policy Benefit, Expected Future Policy Benefit, Cumulative Increase (Decrease) from Cash Flow Change Equity Awards Adjustments Equity Awards Adjustments [Member] Total property & casualty operations Property and Casualty, Commercial Insurance [Member] Total liabilities and equity Liabilities and Equity Employee Stock Option Share-Based Payment Arrangement, Option [Member] Purchases Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases Total property & casualty operations Property, Liability and Casualty Insurance Product Line [Member] Noncontrolling interests Equity, Attributable to Noncontrolling Interest Segments [Axis] Segments [Axis] Other liabilities Increase (Decrease) in Other Operating Liabilities Additional 402(v) Disclosure Additional 402(v) Disclosure [Text Block] Asset Class [Axis] Asset Class [Axis] Estimated Fair Value, Fixed maturities trading Fixed maturities trading Debt Securities, Trading Tabular List, Table Tabular List [Table Text Block] Net Unrealized Gains (Losses) on Investments with an Allowance for Credit Losses AOCI, Gain (Loss), Debt Securities, Available-for-Sale, with Allowance for Credit Loss, Parent [Member] Additional paid-in capital Additional Paid in Capital Ceded reserves, beginning of year Ceded reserves, end of period Reinsurance Recoverable for Unpaid Claims and Claims Adjustments Claim and Claim Adjustment Expense Reserves Liability for Future Policy Benefits and Unpaid Claims Disclosure [Text Block] Catastrophe-related reinsurance reinstatement premiums Catastrophe-Related Reinsurance Reinstatement Premiums Catastrophe-Related Reinsurance Reinstatement Premiums Short-term investments Short-Term Investments [Member] Name Awards Close in Time to MNPI Disclosures, Individual Name Shareholders' equity: Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested Year-end Fair Value of Equity Awards Granted in Covered Year that are Outstanding and Unvested [Member] Debt-to-Value [Axis] Debt-to-Value [Axis] Preferred stock, shares authorized (in shares) Preferred Stock, Shares Authorized Preferred stock Preferred Stock, Value, Issued Loss from catastrophes, net of reinsurance Loss from Catastrophes, Net of Reinsurance Loss from Catastrophes, Net of Reinsurance Adjustment to Compensation: Adjustment to Compensation [Axis] Commercial mortgage-backed Commercial Mortgage-Backed Securities [Member] Reclassification of losses from accumulated other comprehensive loss, after tax Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax Class of Stock [Domain] Class of Stock [Domain] Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] Aggregate Erroneous Compensation Amount Aggregate Erroneous Compensation Amount Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Amount of debt redeemed Extinguishment of Debt, Amount Foreign Currency Translation Accumulated Foreign Currency Adjustment Including Portion Attributable to Noncontrolling Interest [Member] Schedule of Other than Temporary Impairment, Credit Losses Recognized in Earnings [Table] Schedule of Other than Temporary Impairment, Credit Losses Recognized in Earnings [Table] Purchase of subsidiary stock from noncontrolling interests Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests Warranty Insurance Warranty [Member] Insurance Warranty Corporate, Reconciling Items and Eliminations Corporate, Reconciling Items And Eliminations [Member] Corporate, Reconciling Items And Eliminations Aggregate Available Trading Arrangement, Securities Aggregate Available Amount Basis of Presentation Disclosure of Basis of Presentation [Abstract] Disclosure of Basis of Presentation [Abstract] Purchases of limited partnership investments Payments to Acquire Limited Partnership Interests Long-term debt Long-Term Debt and Lease Obligation Name Measure Name Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward] Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward] Interest accretion Liability for Future Policy Benefit, Interest Expense Pay vs Performance Disclosure [Line Items] Adjusted balance, January 1 Balance, end of period at original locked in discount rate Liability for Future Policy Benefit, Expected Net Premium, Original Discount Rate, before Reinsurance, after Cash Flow Change Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Debt Instrument [Line Items] Debt Instrument [Line Items] A&EP Reserves [Abstract] Movement in Liability for Asbestos and Environmental Claims [Abstract] Proceeds from sales of equity securities Proceeds from Sale of Equity Securities, FV-NI Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Debt Securities, Available-for-sale, Allowance for Credit Loss [Table] Debt Securities, Available-for-Sale, Allowance for Credit Loss [Table] Corporate Corporate Segment and Other Operating Segment [Member] Present value of future benefits & expenses Liability for Future Policy Benefit, Expected Future Policy Benefit [Roll Forward] Business combination, consideration transferred Business Combination, Consideration Transferred Retirement Plan Type [Domain] Retirement Plan Type [Domain] Additional Paid-in Capital Additional Paid-in Capital [Member] Entity Filer Category Entity Filer Category Total, Estimated Fair Value Estimated Fair Value Debt Securities, Available-for-Sale, Unrealized Loss Position Insurance related administrative expenses General Insurance Expense Guarantor Obligations, Nature [Domain] Guarantor Obligations, Nature [Domain] A Fitch, A Rating [Member] Name Trading Arrangement, Individual Name Other liabilities Other Liabilities, Fair Value Disclosure Fair value of collateral trust account Collateral Trust Account, Fair Value Disclosure Fair value portion of a collateral trust account established by National Indemnity (NICO) as security for its obligations to CNA Financial Corporation (CNA). Expect of actual variances from expected experience Liability for Future Policy Benefit, Expected Net Premium, Cumulative Increase (Decrease) of Actual Variance from Expected Experience Commercial auto Commercial Auto Insurance [Member] Commercial Auto Insurance Other Investments Other [Member] Investments classified as other. Company Selected Measure Amount Company Selected Measure Amount Investments, Debt and Equity Securities [Abstract] Investments, Debt and Equity Securities [Abstract] Unrealized Gains (Losses) Recognized in Net Income (Loss) on Level 3 Assets and Liabilities Held at June 30 Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss) Net income Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Investment income, operating Gross Investment Income, Operating Non-PEO NEO Non-PEO NEO [Member] Entity Address, Address Line One Entity Address, Address Line One Gross losses Investment Loss, Gross Investment Loss, Gross Total Benefits, Losses and Expenses Income tax expense Income tax (expense) benefit Income Tax Expense (Benefit) Commitments to purchase or fund investments Purchase Obligation Purchases of equity securities Payments to Acquire Equity Securities, FV-NI Amount of cash outflow to acquire investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). Award Timing Method Award Timing Method [Text Block] Balance, June 30 Liability for Future Policy Benefit, Expected Future Policy Benefit, before Reinsurance, after Discount Rate Change Net change in cash Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation Forgone Recovery, Explanation of Impracticability Forgone Recovery, Explanation of Impracticability [Text Block] Spire Marketing LLC Spire Marketing LLC [Member] Spire Marketing LLC Accrued interest receivables on available-for-sale fixed maturity securities Debt Securities, Available-for-Sale, Accrued Interest, after Allowance for Credit Loss Amortization of unrecognized net loss Defined Benefit Plan, Amortization of Gain (Loss) Net income attributable to Loews Corporation Net Income (Loss) Attributable to Parent Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] Location, Statement of Financial Position, Balance [Axis] Location, Statement of Financial Position, Balance [Axis] Discounted cash flow Valuation Technique, Discounted Cash Flow [Member] Statement [Table] Statement [Table] DSCR Greater than or Equal to 1.6x, LTV 55% to 65% Debt Service Coverage Ratio One, Loan-to-value 55 to 65 Percent [Member] Debt service coverage ratio (DSCR) >1.6x and loan-to-value (LTV) ratio between 55% and 65%. The DSCR compares a property's net operating income to its debt service payments, including principal and interest. The LTV ratio compares the current unpaid principal balance of the loan to the estimated fair value of the underlying property collateralizing the loan. Restatement Determination Date: Restatement Determination Date [Axis] Schedule of Changes in AOCI by Component Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] 2025 Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year Liability for future policy benefit, expected future gross premium, discounted, before reinsurance Liability for Future Policy Benefit, Expected Future Gross Premium, Discounted, before Reinsurance Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] Debt Securities, Held-to-Maturity, Credit Quality Indicator [Line Items] Share-Based Payment Arrangement Share-Based Payment Arrangement [Member] Revenues: Revenues [Abstract] Corporate bonds and other Corporate Bonds And Other [Member] Corporate Bonds And Other Basis of Presentation Basis of Presentation and Significant Accounting Policies [Text Block] Pension Benefits Adjustments, Footnote Pension Benefits Adjustments, Footnote [Text Block]