Trading Arrangements, by Individual Trading Arrangements, by Individual [Table] Trading Arrangement: Trading Arrangement [Axis] Maximum Maximum [Member] Potential recoveries Potential Recoveries under Credit Risk Derivatives Represents the potential amount of recoveries under sale of credit protection. Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] Title of 12(b) Security Title of 12(b) Security Amortized cost, net Reported Value Measurement [Member] Debt Securities, Available-for-sale [Table] Debt Securities, Available-for-Sale [Table] Net income applicable to common shareholders, diluted Net Income (Loss) Available to Common Stockholders, Diluted Fair Value Assets and Liabilities Measured on Recurring Basis Unobservable Inputs Gain (Loss) [Table] Fair Value Assets and Liabilities Measured on Recurring Basis Unobservable Inputs Gain (Loss) [Table] Summarization of information required and determined to be disclosed concerning assets and liabilities, including [financial] instruments, which are measured at fair value on a recurring basis using significant unobservable inputs (Level 3). Net change in cash Net Change In Cash Proceeds Managed Collateral The net change in cash from the proceeds managed related to collateral received in conjunction with the entity's securities lending and over-the-counter derivatives. Derivative Instruments, Gain (Loss) [Table] Derivative Instruments, Gain (Loss) [Table] Adjustment to Compensation, Amount Adjustment to Compensation Amount Financial Instrument [Axis] Financial Instrument [Axis] Other assets Other Assets, Fair Value Disclosure Segment Reporting [Abstract] Segment Reporting [Abstract] Protection plans Protection Plans [Member] Protection Plans Short-Duration Insurance Contract, Accident Year 2025 Short-Duration Insurance Contract, Accident Year 2025 [Member] Fixed income securities with unrealized loss position greater than or equal to 20% of amortized cost, net Available for sale Securities, Unrealized Losses Having Loss of Twenty Percent or Higher The amount of unrealized losses that are related to securities with an unrealized loss position greater than 20% of cost or amortized cost. Unearned premiums Increase (Decrease) in Unearned Premiums General [Abstract] General [Abstract] General [Abstract] Benefit Plans Retirement Benefits [Text Block] Derivative Instrument [Axis] Derivative Instrument [Axis] Unrealized net holding gains and losses arising during the period, net of related offsets Other Comprehensive Income (Loss) before Reclassifications, Tax Measurement Frequency [Axis] Measurement Frequency [Axis] U.S. government and agencies US Treasury and Government [Member] Consolidated Entities [Axis] Consolidated Entities [Axis] Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Preferred stock and additional capital paid-in, $1 par value, 25 million shares authorized, 82.0 thousand shares issued and outstanding, $2,050 aggregate liquidation preference Preferred Stock, Including Additional Paid in Capital ABS ABS Asset-Backed Securities [Member] Other comprehensive income (loss), after-tax Other Comprehensive Income (Loss), Net of Tax [Abstract] Consolidated Entities [Domain] Consolidated Entities [Domain] Numerator: Numerator [Abstract] Schedule of Effects of Reinsurance Schedule of Reinsurance Claims Benefits Ceded [Table Text Block] This element may be used as a single block of text to encapsulate entire disclosure, including data and tables for reinsurance claims and benefits ceded. Total unrealized losses Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Allstate Health and Benefits Allstate Health And Benefits [Member] Allstate Health And Benefits Exchange [Domain] Exchange [Domain] Catastrophic Event [Domain] Catastrophic Event [Domain] Loss contingencies, reasonably possible pretax loss exposure in excess of the amount accrued Loss Contingency Reasonably Possible Additional Losses Pretax Estimate Estimate of the reasonably possible pretax loss exposure in excess of the amount accrued for the entity's lawsuits, regulatory inquiries and other legal proceedings. Retirement Benefits [Abstract] Retirement Benefits [Abstract] Outstanding Aggregate Erroneous Compensation Amount Outstanding Aggregate Erroneous Compensation Amount Equity and index contracts Equity and Index Contract [Member] An equity and index contract. Schedule of OTC Cash and Securities Collateral Pledged Schedule Of Cash And Securities Collateral Pledged [Table Text Block] Schedule Of Cash And Securities Collateral Pledged Schedule of Additional Significant Financial Performance Data Schedule of Segment Reporting Information, Additional Information [Table Text Block] This element may be used to capture the additional significant financial performance data for each of the company's reportable segments. Entity Address, City or Town Entity Address, City or Town Total derivatives, fair value, net Derivative, Fair Value, Net Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Schedule of Reinsurance and Indemnification Recoverables Schedule Of Reinsurance Recoverable For Paid And Unpaid Claims And Claims Adjustments [Table Text Block] Schedule of Reinsurance Recoverable for Paid and Unpaid Claims and Claims Adjustments [Table Text Block] Peer Group Total Shareholder Return Amount Peer Group Total Shareholder Return Amount Incurred claims and claims expense related to: Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims [Abstract] Accident and health insurance premiums and contract charges Ceded Premiums and Contract Charges Represents the amount of premiums and contract charges related to life insurance, accident and health insurance and annuity contracts that are assumed and earned by another insurer as a result of reinsurance arrangements. Significant other observable inputs (Level 2) Fair Value, Inputs, Level 2 [Member] Total Shareholder Return Vs Peer Group Total Shareholder Return Vs Peer Group [Text Block] Other comprehensive income (loss), after-tax Other Comprehensive Income (Loss), Net of Tax Non-Rule 10b5-1 Arrangement Terminated Non-Rule 10b5-1 Arrangement Terminated [Flag] 90 days or greater past due Financial Asset, Equal to or Greater than 90 Days Past Due [Member] Schedule of Reportable Segment Total Assets, Investments and Deferred Policy Acquisition Costs Segment Reporting, Reconciliation of Asset by Segment to Consolidated [Table Text Block] Other segment expenses Other Expenses Discount rate Defined Benefit Plan, Benefit Obligation, (Increase) Decrease For Remeasurement Due To Change In Weighted Average Discount Rate Defined Benefit Plan, Benefit Obligation, (Increase) Decrease For Remeasurement Due To Change In Weighted Average Discount Rate Securities collateral (received) pledged Derivative Asset, Subject to Master Netting Arrangement, Collateral, Obligation to Return Security Not Offset Pledged by the Company Margin Deposit Assets Other revenue Insurance Commissions and Fees Investment Income [Table] Investment Income [Table] Gross and net information about the liabilities subject to master netting arrangements Offsetting Assets and Liabilities [Line Items] Transfers into Level 3 Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers Into Level 3 Fixed income securities Available for sale Fixed Income Securities Unrealized Gain (Loss) Included in Other Comprehensive Income The amount of unrealized gains (losses) included in accumulated other comprehensive income on fixed income securities which are categorized neither as held-to-maturity nor trading securities, as a result of fair value exceeding (under) its amortized cost, as of the balance sheet date. Schedule of Reportable Segments Expense Information Used in Measure for Segment Profit or Loss Segment Reporting [Table Text Block] Pre-tax Other Comprehensive Income (Loss), before Tax [Abstract] Credit Derivatives Credit Derivatives [Line Items] Fixed income securities with unrealized loss position less than 20% of amortized cost, net Available for sale Securities, Unrealized Losses Having Loss of Less than Twenty Percent The amount of unrealized losses that are related to securities with an unrealized loss position less than 20% of cost or amortized cost. Guarantor Obligations [Line Items] Guarantor Obligations [Line Items] Allowance Beginning balance Ending balance Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest Document Period End Date Document Period End Date Bank Loan Acquisition Period [Domain] Bank Loan Acquisition Period [Domain] Bank Loan Acquisition Period Preferred stock, shares outstanding (in shares) Preferred Stock, Shares Outstanding NAIC 5-6 / CCC and below Standard & Poor's, CCC- Rating [Member] Cumulative amount incurred to date for active programs Restructuring and Related Cost, Cost Incurred to Date Gross realized losses Debt Securities, Available-for-Sale, Realized Loss Treasury stock, at cost (646 million and 640 million shares) Treasury Stock, Common, Value Fair value Debt Securities, Available-for-Sale, Maturity, Fair Value, Rolling Maturity [Abstract] Supplemental Cash Flow Information Cash Flow, Supplemental Disclosures [Text Block] Options Equity and Index Contracts Options and Warrants [Member] An investment that follows an index, commodity or basket of assets that trades like stock on an exchange. Total accumulated other comprehensive (loss) income Accumulated Other Comprehensive Income (Loss), Net of Tax Entity Shell Company Entity Shell Company Consolidation Items [Domain] Consolidation Items [Domain] Total gains (losses) included in: net income Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings Derivative instruments Derivative Instruments, Unrealized Gain Included in Other Comprehensive Income The amount of unrealized gains included in accumulated other comprehensive income on derivative instruments, as of the balance sheet date. Mortgage loans Mortgage loans Mortgages [Member] Due after five years through ten years Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Amortized Cost Earnings per Common Share Earnings Per Share [Text Block] Earnings per common share: Earnings Per Share [Abstract] Document Fiscal Period Focus Document Fiscal Period Focus Peer Group Issuers, Footnote Peer Group Issuers, Footnote [Text Block] Total liabilities Liabilities Trading Symbol Trading Symbol Percentage of claims Prior Year Claims and Claims Adjustment Expense, Percentage Prior Year Claims and Claims Adjustment Expense, Percentage Fixed income securities, at fair value (amortized cost, net $60,902 and $58,730) Fixed income securities, at fair value Fair value Fair value Debt Securities, Available-for-Sale, Excluding Accrued Interest Transfers out of Level 3 Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3 2025 Acquisition 2025 [Member] Acquisition 2025 Purchases of property and equipment, net Payments to Acquire Property, Plant, and Equipment Company Selected Measure Name Company Selected Measure Name Total gains (losses) included in: OCI Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss) Fixed income securities Payments to Acquire Debt Securities, Available-for-Sale Gross asset fair value of contracts containing credit-risk-contingent features and subject to MNAs Derivative Gross Asset Fair Value with Credit Risk Contingent Features Fair value of derivative asset, presented on a gross basis containing credit risk contingent features and which is subject to master netting arrangements. Equity securities, at fair value, cost Equity securities Equity Securities, FV-NI, Cost Reserve for property and casualty insurance claims and claims expense Reserve for property and casualty insurance claims and claims expense Beginning balance Ending balance Liability for Claims and Claims Adjustment Expense Cash flows from operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract] Equity Valuation Assumption Difference, Footnote Equity Valuation Assumption Difference, Footnote [Text Block] Transfers Out of Level 3 Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3 Schedule of Net Investment Income Investment Income [Table Text Block] Adjustments to liability Restructuring Reserve, Accrual Adjustment ABS and MBS Debt Securities, Available-for-Sale, Maturity, without Single Maturity Date, Amortized Cost Other operating assets and liabilities Increase (Decrease) in Other Operating Assets and Liabilities, Net Pledged to the Company Cash and Securities Pledged as Collateral, from Counterparties This element represents cash and securities pledged as collateral from counterparties. Operating lease, payments Operating Lease, Payments Award Timing Predetermined Award Timing Predetermined [Flag] Schedule of Components of Other Comprehensive Income (Loss) on a Pre-Tax and After-Tax Basis Comprehensive Income (Loss) [Table Text Block] Pension and other postretirement remeasurement (gains) losses Defined Benefit Plan, Remeasurement Gain (Loss) Defined Benefit Plan, Remeasurement Gain (Loss) Sales Debt Securities, Gain (Loss) Reserve for Property-Liability Insurance Claims and Claims Expense [Abstract] Reserve for Property-Liability Insurance Claims and Claims Expense [Abstract] Reserve for Property-Liability Insurance Claims and Claims Expense [Abstract] Adjustment To PEO Compensation, Footnote Adjustment To PEO Compensation, Footnote [Text Block] Equity incentive plans activity, net APIC, Share-Based Payment Arrangement, Increase for Cost Recognition Property and casualty insurance claims and claims expense Policyholder Benefits and Claims Incurred, Net Quoted prices in active markets for identical assets (Level 1) Fair Value, Inputs, Level 1 [Member] Net beginning balance Net ending balance Liability for Unpaid Claims and Claims Adjustment Expense, Net Due after ten years Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value Capital transactions for noncontrolling interest Noncontrolling Interest, Increase From Capital Transaction Noncontrolling Interest, Increase From Capital Transaction Above 1.50 Debt Service Coverage Ratio above 1.50 [Member] This element represents the information pertaining to mortgage loans on real estate having a debt service coverage ratio above 1.50 Restricted stock units (non-participating) and performance stock awards (in shares) Incremental Common Shares Attributable to Restricted Stock Units Aggregate awards of restricted stock to be issued to an employee under a share-based compensation arrangement considered for purposes of computing diluted earnings per share. Operating cash flow provided (used) Net Cash Provided by (Used in) Operating Activities, Liabilities for Collateral The net operating cash flow provided by (used in) the net change in liabilities for collateral. Accident and health insurance premiums and contract charges Accident, Health And Life Insurance Product Line [Member] Accident, Health And Life Insurance Product Line Income tax (expense) benefit on Allstate Protection and Run-off Property-Liability and reconciling items Income Tax Expense (Benefit), Reconciling Items Income Tax Expense (Benefit), Reconciling Items Preferred stock, par value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Commitments to invest in limited partnership interests Commitments to Invest in Limited Partnership Interests This element represents commitments to acquire financial interests or instruments, to allow for additional participation in certain limited partnership investments. Because the equity investments in the limited partnerships are not actively traded, it is not practical to estimate the fair value of these commitments. Number of counter-parties Number of Counterparties The number of counterparties to which the entity has counterparty credit exposure related to derivative contracts. Non-cash investing activities, right-of-use asset, property and equipment obtained Noncash Investing Activities, Right-Of-Use Asset, Property And Equipment, Obtained In Exchange For Operating Lease Liability Noncash Investing Activities, Right-Of-Use Asset, Property And Equipment, Obtained In Exchange For Operating Lease Liability Claims and claims expense paid related to: Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid [Abstract] Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Contractholder fund withdrawals Withdrawal from Contract Holders Funds Intersegment premiums and service fees Intersegment Premiums And Service Fees Intersegment Premiums And Service Fees Schedule of Rollforward of Credit Loss Allowance for Fixed Income Securities, Mortgage Loans and Bank Loans Allowance For Credit Loss [Table Text Block] Allowance for Credit Loss [Table Text Block] Unamortized pension and other postretirement prior service credit Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax Investments Investment in Debt and Equity Securities and Other Trading Assets [Text Block] Ceded losses incurred Reinsurance Ceded Amount Represents the amount of reinsurance ceded under various contracts. Other liabilities Other Liabilities Counterparty Netting and Collateral Right To Reclaim Cash Offset Other Liabilities Counterparty Netting and Collateral Right To Reclaim Cash Offset Dividends paid on common stock Payments of Ordinary Dividends, Common Stock Unrealized net gains (losses) Unrealized Net Gains (Losses) on Investments [Abstract] Expiration Date Trading Arrangement Expiration Date Income from operations before income tax expense Income (Loss) from Operations before Income Tax Expense (Benefit) Sum of operating profit and non-operating income (expense) and income (loss) from equity method investments before income taxes. Total credit losses by asset type Allowance For Credit Loss, Credit Loss By Asset Type Allowance For Credit Loss, Credit Loss By Asset Type Total equity Balance, beginning of period Balance, end of period Equity, Including Portion Attributable to Noncontrolling Interest Aggregate Pension Adjustments Service Cost Aggregate Pension Adjustments Service Cost [Member] Derivative [Table] Derivative [Table] Interest rate contracts Interest Rate Financial Futures Contracts [Member] Derivative instrument whose primary underlying risk is tied to the right to receive or pay a sum of money at a given interest rate. Earnings per common share: Earnings Per Share Reconciliation [Abstract] Real estate Real Estate Loan [Member] BB and lower Standard Poors BB and Lower Rating [Member] BB and lower rating as defined by the external credit rating agency, Standard and Poor's. Cash flows from investing activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract] Net change in liabilities Net Change in Liabilities for Collateral [Abstract] Schedule of Reportable Segments Revenue Information Schedule of Business Segments Revenue Disclosure [Table Text Block] The schedule of revenues by segment. Asset derivatives Derivative Asset [Abstract] Segments [Domain] Segments [Domain] Interest rate swap agreements Interest Rate Swap [Member] Schedule of Bank Loans Amortized Cost by Credit Rating and Year of Origination Bank Loans Amortized Cost By Credit Quality And Year Of Origination [Table Text Block] Bank loans amortized cost by credit quality and year of origination [Table Text Block] PEO Actually Paid Compensation Amount PEO Actually Paid Compensation Amount Mortgage loans Payments to Purchase Mortgage Loans The cash outflow used to purchase loans that are secured with real estate mortgage. Allstate Protection Property Liability Allstate Protection and Run-off Property-Liability Property Liability [Member] Property-liability segment includes the Allstate Protection and the discontinued lines and coverage segments. Dividends on common stock (declared per share of $1.08, $1.00, $2.16, and $2.00) Dividends, Common Stock, Cash Total Allstate shareholders’ equity Total Allstate shareholders’ equity Equity, Attributable to Parent Entity Listings, Exchange [Axis] Entity Listings, Exchange [Axis] Futures Equity and Index Contracts Financial Futures Contracts [Member] Derivative instrument whose primary underlying risk is tied to share prices for financial futures contracts. Assets Assets Assets [Abstract] Other investments, net Other investments, net Other investments Other Investments Options Equity and Index Contracts Options [Member] An investment that follows an index or commodity that trades like stock on an exchange Schedule of Gross Unrealized Losses by Unrealized Loss Position and Credit Quality Financing Receivable Credit Quality Indicators [Table Text Block] Non-recurring basis Fair Value, Nonrecurring [Member] Insider Trading Policies and Procedures [Line Items] Less than 12 months Less than Twelve Months [Abstract] Number of reportable segments not disclosed flag NumberOfReportableSegmentsNotDisclosedFlag NumberOfReportableSegmentsNotDisclosedFlag Liabilities Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Loss adjustment expenses, net of reinsurance Total incurred Losses from catastrophes, net of recoveries Liability for Unpaid Claims and Claims Adjustment Expense, Incurred Claims Financing Receivable Portfolio Segment [Domain] Financing Receivable Portfolio Segment [Domain] Total recurring Level 3 liabilities Fair Value Liabilities, Measured On Recurring Basis, Change In Unrealized Gain (Loss) Included In Earnings Fair Value Liabilities, Measured On Recurring Basis, Change In Unrealized Gain (Loss) Included In Earnings Anti-dilutive share-based awards excluded from diluted earnings per common share (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Entity Central Index Key Entity Central Index Key Additional capital paid-in Additional Paid in Capital, Common Stock Schedule of Guarantor Obligations [Table] Guarantor Obligation [Table] OTC derivatives Over-the-Counter [Member] 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] Nationwide Reinsurance Program Nationwide Reinsurance Program [Member] Nationwide Reinsurance Program Unrealized net holding gains and losses arising during the period, net of related offsets Other Comprehensive Income (Loss), before Reclassifications, Net of Tax Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Investments [Line Items] Schedule of Investments [Line Items] Reinsurance and indemnification recoverables, net Reinsurance recoverables, net Reinsurance and indemnification recoverables, net Reinsurance And Indemnification Recoverables, Net Reinsurance And Indemnification Recoverables, Net Dividends on preferred stock Dividends, Preferred Stock, Cash Less than 90 days past due Financial Asset, Less Than 90 Days Past Due [Member] Financial Asset, Less Than 90 Days Past Due Operating cash flow (used) provided Net Cash Provided by Used in Operating Activities Proceeds Managed Collateral The net operating cash flow provided or used related to collateral received in conjunction with the entity's securities lending and over-the-counter derivatives. Participating Mortgage Loans [Axis] Mortgage Acquisition Period [Axis] Mortgage Acquisition Period [Axis] 1.26 - 1.50 Debt Service Coverage Ratio below 1.26 to 1.50 [Member] This element represents the information pertaining to mortgage loans on real estate having a debt service coverage ratio between 1.26 to 1.50 Accumulated other comprehensive income (loss) AOCI Attributable to Parent [Member] Corporate - public Corporate - public Corporate Debt Securities, Public [Member] Corporate Debt Securities, Public [Member] All Individuals All Individuals [Member] Fair Value Assets Measured on Recurring Basis Unobservable Input Reconciliation Calculation Rollforward Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Schedule of Net Appreciation (Decline) Recognized In net Income For Assets That Are Still Held Realized Gain (Loss) on Investments [Table Text Block] Mortgage loans Proceeds from Collection of Mortgage Loans The cash inflow from collections of repayments from borrowers on loans that are secured with real estate mortgages. Remeasurement of plan assets (gains) losses Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Remeasurement Plan Assets Gain (Loss) Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Remeasurement Plan Assets Gain (Loss) Statement Statement [Line Items] Total assets Assets Assets Schedule of Defined Benefit Plans Disclosures [Table] Defined Benefit Plan [Table] Other assumptions Defined Benefit Plan, Benefit Obligation, (Increase) Decrease For Remeasurement Due To Change In Other Assumptions Defined Benefit Plan, Benefit Obligation, (Increase) Decrease For Remeasurement Due To Change In Other Assumptions Interest expense Interest Expense, Operating Valuation change of equity investments Equity Securities, FV-NI, Realized Gain (Loss) Internal Credit Assessment [Domain] Internal Credit Assessment [Domain] Operating segments Operating Segments [Member] Credit default swaps - selling protection Credit Default Swap, Selling Protection [Member] Gross unrealized gains Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax ABS and MBS Debt Securities, Available-for-Sale, Maturity, without Single Maturity Date, Fair Value PEO PEO [Member] Assets held for sale Assets Held For Sale [Member] Assets Held For Sale Goodwill Goodwill Retirement Plan Type [Axis] Retirement Plan Type [Axis] Fixed income securities Fixed income securities Fixed Income Securities [Member] Forgone Recovery due to Violation of Home Country Law, Amount Forgone Recovery due to Violation of Home Country Law, Amount Retained income Retained Earnings [Member] Total Operating Expenses Total liability derivatives, number of contracts Derivative Liability, Number of Instruments Held Other investments Other Investments, Gross Asset and Right to Reclaim Cash, Offset Other Investments, Gross Asset and Right to Reclaim Cash, Offset Increase (decrease) in equity Increase (Decrease) in Stockholders' Equity [Roll Forward] Common stock, shares outstanding (in shares) Common Stock, Shares, Outstanding Award Timing Disclosures [Line Items] Unrealized foreign currency translation adjustments Accumulated Foreign Currency Adjustment Attributable to Parent [Member] Schedule of Financial Instruments Not Carried at Fair Value Fair Value, by Balance Sheet Grouping [Table Text Block] Short-term investments Available For Sale Short-Term Investments, Unrealized Gain Included In Other Comprehensive Income Available For Sale Short-Term Investments, Unrealized Gain Included In Other Comprehensive Income Corporate Corporate bonds Corporate Debt Securities [Member] Net income applicable to common shareholders per common share - Diluted (in dollars per share) Earnings per common share - Diluted (in dollars per share) Earnings Per Share, Diluted Internal Credit Assessment [Axis] Internal Credit Assessment [Axis] Amortization of purchased intangibles Amortization of purchased intangibles Intangible Asset, Finite-Lived, Amortization Expense Counterparty and cash collateral netting Derivative Liability Counterparty Netting and Collateral Right To Reclaim Cash Offset Represents the amount of counterparty netting and the amount of right to receive cash collateral under master netting arrangements offset against derivative liabilities. A+ Standard & Poor's, A+ Rating [Member] Less: reclassification adjustment of realized capital gains and losses Reclassification from AOCI, Current Period, Tax Schedule of Restructuring Activity Schedule of Restructuring Reserve by Type of Cost [Table Text Block] Municipal Not Rated by Third Party Credit Rating Agencies Municipal Not Rated by Third Party Credit Rating Agencies [Member] Represents the municipal securities not rated by third party credit rating agencies. Financial assets Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] Bank loans Bank Loans Categorized under Other Investments Represents the portion of other investments categorized as bank loans, as of the balance sheet date. Equity Awards Adjustments, Footnote Equity Awards Adjustments, Footnote [Text Block] Credit losses on securities for which credit losses not previously reported Debt Securities, Available-for-Sale, Excluding Accrued Interest, Allowance for Credit Loss, Not Previously Recorded Subtotal Available for sale Securities, Debt Maturities with Single Maturity Date Fair Value This item represents the total of all debt securities grouped by maturity dates excluding asset-backed securities, residential mortgage-backed securities and commercial mortgage-backed securities, at fair value, which are classified neither as held-to-maturity nor trading securities. Accident, health and other policy benefits Accident, health and other policy benefits Accident And Health Insurance Contract Benefits, Net of Reinsurance Recoveries Accident And Health Insurance Contract Benefits, Net of Reinsurance Recoveries Subsegments [Domain] Subsegments [Domain] Sales Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales Write-offs Reinsurance, Loss on Uncollectible Accounts in Period, Amount Net amount Derivative Liability, Including Not Subject to Master Netting Arrangement, after Offset and Deduction Due after one year through five years Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Amortized Cost Short-term investments Available For Sale Short-Term Investments, Unrealized Loss Included In Other Comprehensive Income Available For Sale Short-Term Investments, Unrealized Loss Included In Other Comprehensive Income Total included in net income Fair Value Assets and Liabilities Measured on Recurring Basis Change in Unrealized Gain (Loss) Included in Earnings This item represents the amount of the total change in unrealized (holding) gains or losses for the period which are included in the statement of income (or changes in net assets). Such unrealized (holding) gains or losses relate to those assets and liabilities still held at the reporting date for which fair value is measured on a recurring basis using significant unobservable inputs (Level 3). Costs and expenses Defined Benefit Plan, Other Operating Costs And Expenses Defined Benefit Plan, Other Operating Costs And Expenses Below investment grade fixed income securities Below investment grade fixed income securities Below Investment Grade Fixed Income Securities [Member] Below investment grade is defined as a security not meeting the criteria for investment grade securities. Foreign government Debt Security, Government, Non-US [Member] Rule 10b5-1 Arrangement Adopted Rule 10b5-1 Arrangement Adopted [Flag] Equity securities Equity Securities [Member] Fair Value Recurring Basis Unobservable Input Reconciliation Liability Gain Loss Statement Of Income Extensible List Not Disclosed Flag Fair Value Recurring Basis Unobservable Input Reconciliation Liability Gain Loss Statement Of Income Extensible List Not Disclosed Flag Fair Value Recurring Basis Unobservable Input Reconciliation Liability Gain Loss Statement Of Income Extensible List Not Disclosed Flag Common stock, shares issued (in shares) Common Stock, Shares, Issued Balance at beginning of period Balance at end of period Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value Claim payments outstanding Claim Payments Outstanding Liability as of the balance sheet date for benefit claims that have been paid but the payment has not yet cleared. Payments and non-cash charges Payments For Restructuring And Other Non-Cash Charges Payments For Restructuring And Other Non-Cash Charges Unrealized losses Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss Other Comprehensive Income (Loss) Comprehensive Income (Loss) Note [Text Block] Insurance Product Line [Domain] Product and Service [Domain] Catastrophe Catastrophe losses Catastrophe [Member] Variable Interest Entity [Line Items] Variable Interest Entity [Line Items] Deferred income taxes Deferred Income Tax Liabilities, Net Compensation Actually Paid vs. Other Measure Compensation Actually Paid vs. Other Measure [Text Block] Gains (losses) from valuation and settlements reported on derivatives Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net Termination Date Trading Arrangement Termination Date Investment grade fixed income securities Investment grade fixed income securities Investment Grade Fixed Income Securities [Member] Investment grade is defined as a security having a rating from the National Association of Insurance Commissioners ("NAIC") of 1 or 2; a rating of Aaa, Aa, A or Baa from Moody's, a rating of AAA, AA, A or BBB from Standard and Poor's, Fitch or Dominion, or aaa, aa, a or bbb from A.M. Best; or a comparable internal rating if an externally provided rating is not available. 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] Unamortized pension and other postretirement prior service credit Change in unamortized pension and other postretirement prior service credit Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax Current year Current Year Claims and Claims Adjustment Expense Net amount Derivative Asset, Including Not Subject to Master Netting Arrangement, after Offset and Deduction 2026 Acquisition, Current [Member] Acquisition, Current Fair Value as of Grant Date Award Grant Date Fair Value Expense incurred Increase (Decrease) in Restructuring Reserve Total recurring Level 3 assets Fair Value Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss) Included in Earnings This item represents the amount of the total change in unrealized (holding) gains or losses for the period which are included in the statement of income (or changes in net assets). Such unrealized (holding) gains or losses relate to those assets still held at the reporting date for which fair value is measured on a recurring basis using significant unobservable inputs (Level 3). Transaction Market Method [Domain] Transaction Market Method [Domain] Pay vs Performance Disclosure, Table Pay vs Performance [Table Text Block] Arrangement Duration Trading Arrangement Duration Consolidation Items [Axis] Consolidation Items [Axis] Entity Address, Postal Zip Code Entity Address, Postal Zip Code Entity Registrant Name Entity Registrant Name Unrealized losses Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss Beginning balance Ending balance Reinsurance Recoverable, Allowance for Credit Loss Insider Trading Policies and Procedures Not Adopted Insider Trading Policies and Procedures Not Adopted [Text Block] Total revenues Total revenues Revenues Investments reported at NAV Alternative Investment Forgone Recovery due to Expense of Enforcement, Amount Forgone Recovery due to Expense of Enforcement, Amount Homeowners Homeowners Home Owners [Member] Represents homeowners insurance to individuals in United States and Canada. All Award Types Award Type [Domain] Fair Value of Assets and Liabilities Fair Value Disclosures [Text Block] CHICAGO STOCK EXCHANGE, INC NYSE TEXAS, INC. [Member] Significant unobservable inputs (Level 3) Fair Value, Inputs, Level 3 [Member] Deferred policy acquisition costs Deferred policy acquisition costs Deferred Policy Acquisition Costs and Present Value of Future Insurance Profits, Net Reported to NAV Fair Value Measured at Net Asset Value Per Share [Member] Specialty lines Specialty Lines [Member] Specialty Lines Other assets, net Other assets Other Assets Gross liability fair value of contracts containing credit-risk-contingent features Derivative Gross Liability Fair Value with Credit Risk Contingent Features Fair value of derivative liabilities, presented on a gross basis containing credit risk contingent features. Service cost Defined Benefit Plan, Service Cost, Net Defined Benefit Plan, Service Cost, Net Liability Class [Axis] Liability Class [Axis] Offsetting Assets and Liabilities [Table] Offsetting Assets and Liabilities [Table] Disclosure of information about derivative and financial assets and liabilities that are subject to offsetting, including enforceable master netting arrangements. Protection Services Protection Services [Member] Protection Services Shares acquired Treasury Stock, Value, Acquired, Cost Method Cash at beginning of period Cash at end of period Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation 12 months or more Twelve Months or More [Abstract] Roadside assistance Roadside Assistance [Member] Roadside Assistance [Member] Schedule of Change in Unrealized Net Capital Gains (Losses) Schedule of Change in Unrealized Net Capital Gains and Losses [Table Text Block] This item represents the schedule of change in unrealized net capital gains and losses by type of securities. Effects of Reinsurance [Table] Effects of Reinsurance [Table] Non-NEOs Non-NEOs [Member] Due after ten years Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Amortized Cost Schedule of Derivative CDS Notional Amount by Credit Rating and Fair Value of Protection Sold Disclosure of Credit Derivatives [Table Text Block] Net change in fixed income securities Net Change In Fixed Income Term Investments Of Proceeds Managed Collateral Net Change In Fixed Income Term Investments Of Proceeds Managed Collateral Schedule of Net Gains (Losses) on Investments and Derivatives by Transaction Type Schedule of Gain (Loss) on Investments by Transaction Type [Table Text Block] This item represents the schedule of realized gains and losses reported in the statement of income by type of transactions. Total Realized Gain (Loss), Fair Value Recognized In Net Income Realized Gain (Loss), Fair Value Recognized In Net Income Non-catastrophe losses Excluding catastrophe losses Non Catastrophe Reestimates [Member] Represents adjustments to the reserves for unpaid claims and claims adjustment expense resulting from non-catastrophe loss re-estimates. Noncatastrophic Event [Axis] Noncatastrophic Event [Axis] Treasury stock purchases Payments for Repurchase of Common Stock MBS MBS Collateralized Mortgage-Backed Securities [Member] Statistical Measurement [Axis] Statistical Measurement [Axis] Award Type Award Type [Axis] Interest rate contracts Interest Rate Contract [Member] Named Executive Officers, Footnote Named Executive Officers, Footnote [Text Block] Fixed income securities, at fair value, amortized cost Amortized cost, net Debt Securities, Available-for-Sale, Amortized Cost, Excluding Accrued Interest, after Allowance for Credit Loss Retained income Retained Earnings (Accumulated Deficit) Restructuring and Related Activities [Abstract] Restructuring and Related Activities [Abstract] Insurance Product Line [Axis] Product and Service [Axis] Fair value Credit Risk Derivatives, at Fair Value, Net Awards Close in Time to MNPI Disclosures Awards Close in Time to MNPI Disclosures [Table] Pension benefits Pension Plan [Member] Common Stock, par value $.01 per share Common stock par value Common Stock [Member] Employee costs Employee Severance [Member] Short-term, at fair value, amortized cost Other Short Term Investments, Amortized Cost The amortized cost of short-term investments, net of adjustments for other-than-temporary impairments, if any. Derivative Contract [Domain] Derivative Contract [Domain] Total asset derivatives, number of contracts Derivative Asset, Number of Instruments Held Schedule of OTC Derivatives Counterparty Credit Exposure by Counterparty Credit Rating Schedule of Derivative Counterparty Credit Exposure [Table Text Block] Schedule of counterparty credit exposure by counterparty credit rating. Remeasurement of plan assets Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Remeasurement Of Plan Assets Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Remeasurement Of Plan Assets Total past due before allowance Financial Asset, Past Due [Member] Total liabilities and equity Liabilities and Equity Net gains (losses) on investments and derivatives Net (gains) losses on investments and derivatives Realized Investment Gains (Losses) Employee Stock Option Share-Based Payment Arrangement, Option [Member] Purchases Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases Less: reclassification adjustment of realized capital gains and losses Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax Noncontrolling interest Equity, Attributable to Noncontrolling Interest Property and casualty insurance premiums Property and casualty insurance premiums earned Property, Liability and Casualty Insurance Product Line [Member] Segments [Axis] Segments [Axis] Additional 402(v) Disclosure Additional 402(v) Disclosure [Text Block] Asset Class [Axis] Asset Class [Axis] Schedule of Other investments by Asset Type Schedule Of Other Investments, By Type [Table Text Block] Schedule of Other Investments, By Type [Table Text Block] Restructuring and related charges Restructuring Charges Tabular List, Table Tabular List [Table Text Block] AA Standard & Poor's, AA Rating [Member] Less: recoverables Plus: recoverables Unpaid losses estimated (including IBNR) Reinsurance Recoverable for Unpaid Claims and Claims Adjustments Schedule of Gross Unrealized Losses and Fair Value by Type and Length of Time Held in a Continuous Unrealized Loss Position Unrealized Gain (Loss) on Investments [Table Text Block] Reinsurance and indemnification recoverables, net Increase (Decrease) in Reinsurance Recoverable 1.0 - 1.25 Debt Service Coverage Ratio below 1.0 to 1.25 [Member] This element represents the information pertaining to mortgage loans on real estate having a debt service coverage ratio between 1.0 to 1.25. Credit Derivatives Contract Type [Axis] Credit Derivatives Contract Type [Axis] Name Awards Close in Time to MNPI Disclosures, Individual Name 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] Due after one year through five years Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Fair Value Fair Value by Liability Class [Domain] Fair Value by Liability Class [Domain] Financing Receivable Portfolio Segment [Axis] Financing Receivable Portfolio Segment [Axis] Schedule of Pension and Postretirement Benefits Remeasurement Gains and Losses Schedule of Defined Benefit Plans Disclosures [Table Text Block] Series J Preferred Stock Series J Preferred Stock [Member] Series J Preferred Stock Adjustment to Compensation: Adjustment to Compensation [Axis] Less: reclassification adjustment of realized capital gains and losses Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax Restructuring Cost and Reserve [Line Items] Restructuring Cost and Reserve [Line Items] Rule 10b5-1 Arrangement Terminated Rule 10b5-1 Arrangement Terminated [Flag] Aggregate Erroneous Compensation Amount Aggregate Erroneous Compensation Amount Accumulated other comprehensive income (loss): Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract] Hedging Designation [Axis] Hedging Designation [Axis] Company Restructuring Restructuring and Related Activities Disclosure [Text Block] Assets at fair value Total assets at fair value Assets, Fair Value Disclosure Schedule of Activities Resulting from Management of Proceeds Schedule of Supplemental Cash Flow Information from Collateralized Securities Received [Table Text Block] This element may be used to capture the complete disclosure pertaining to supplemental cash flow information about collateral received. Name Measure Name Pay vs Performance Disclosure [Line Items] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Liability for collateral Liabilities for collateral, beginning of period Liabilities for collateral, end of period Obligation to Return Collateral Securities Lending and Derivatives The liability to return cash and securities received as collateral in conjunction with securities lending and over-the-counter derivatives. Number of  issues Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions Equity securities Proceeds from Sale of Equity Securities, FV-NI Corporate Corporate Segment and Other Operating Segment [Member] Common stock additional capital paid-in Additional Paid-in Capital [Member] Name Trading Arrangement, Individual Name Transfer from investments Transfer from Investments Investment purchases Payments to Acquire Investments [Abstract] Mortgage Acquisition Period [Domain] Mortgage Acquisition Period [Domain] [Domain] for Mortgage Acquisition Period [Axis] Derivative instruments Derivative Instruments, Unrealized Loss Included in Other Comprehensive Income The amount of unrealized losses included in accumulated other comprehensive income on derivative instruments, as of the balance sheet date. Preferred stock measured at cost Preferred Stock, Measured At Cost Preferred Stock, Measured At Cost Less: Cash classified as assets held for sale at end of period Disposal Group, Including Discontinued Operation, Cash Company Selected Measure Amount Company Selected Measure Amount Denominator: Denominator [Abstract] Bank Loan Acquisition Period [Axis] Bank Loan Acquisition Period [Axis] Bank Loan Acquisition Period Non-PEO NEO Non-PEO NEO [Member] Proceeds from sales Proceeds from Sale of Investments [Abstract] Effect of dilutive potential common shares Dilutive Securities, Effect on Basic Earnings Per Share [Abstract] Award Timing Method Award Timing Method [Text Block] Net increase 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] Amounts recognized for: Amount Recognized in Unrealized Net Capital Gains and Losses [Abstract] Total liability derivatives, notional amount Derivative Liability, Notional Amount Net income attributable to Allstate Net Income (Loss) Attributable to Parent Erroneous Compensation Analysis Erroneous Compensation Analysis [Text Block] Maximum amount of additional exposure for contracts with credit-risk-contingent features if all features were triggered concurrently Additional Collateral, Aggregate Fair Value, Net Additional Collateral, Aggregate Fair Value, Net Restatement Determination Date: Restatement Determination Date [Axis] NAIC 2 / BBB BBB Standard & Poor's, BBB Rating [Member] NAIC 3 / BB Standard & Poor's, BB Rating [Member] Remeasurement of projected benefit obligation Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) Schedule of Mortgage Loans Amortized Cost by Debt Service Coverage Ratio Distribution and Year of Origination Mortgage Loans Amortized Cost By Debt Service Coverage Ratio Distribution And Year Of Origination [Table Text Block] Mortgage Loans Amortized Cost By Debt Service Coverage Ratio Distribution And Year Of Origination [Table Text Block] Total gains (losses) included in: OCI Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss) Other liabilities and accrued expenses Other Liabilities And Accrued Expenses Other Liabilities And Accrued Expenses Mortgage loans, net Mortgage loans, net Amortized cost, net Mortgage loans Mortgage Loans on Real Estate, Commercial and Consumer, Net Reinsurance Disclosures [Abstract] Reinsurance Disclosures [Abstract] Revenues Revenues [Abstract] Collateral posted under MNAs for contracts containing credit-risk contingent features Collateral posted under MNAs for contracts containing credit-risk-contingent features Collateral Already Posted, Aggregate Fair Value Non-deferrable commissions Non-Deferrable Commissions Non-Deferrable Commissions Pension Benefits Adjustments, Footnote Pension Benefits Adjustments, Footnote [Text Block] Other assets Other Asset Class [Member] Other Asset Class Deferred income taxes OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment, Tax Statistical Measurement [Domain] Statistical Measurement [Domain] Property and casualty insurance premiums earned Ceded Premiums Earned Document Fiscal Year Focus Document Fiscal Year Focus Liability derivatives, gross asset Counter-party netting Derivative Liability, Subject to Master Netting Arrangement, Asset Offset Cash collateral (received) pledged Derivative Liability, Subject to Master Netting Arrangement, Collateral, Right to Reclaim Cash Offset Depreciation, amortization and other non-cash items Depreciation, Amortization and Accretion, Net Reductions to costs and expenses due to reinsurance ceded amounts Reinsurance Claims Benefits Ceded [Abstract] Schedule of Carrying Value for Limited Partnership Interests Schedule of Investments in and Advances to Affiliates, Schedule of Investments [Table Text Block] Restatement Determination Date Restatement Determination Date Limited partnership interests Limited partnership interests Total 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 Due after five years through ten years Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling after 5 through 10 Years, Fair Value Foreign currency contracts Foreign Currency Forwards [Member] Represents information pertaining to contracts negotiated between two parties to purchase and sell a specific quantity of foreign currency at a price specified at origination of the contract, with delivery and settlement at a specified future date. Amendment Flag Amendment Flag Debt and Equity Securities, FV-NI [Line Items] Debt and Equity Securities, FV-NI [Line Items] Credit default contracts Credit Default Swap [Member] Received by the Company Margin Deposit Liabilities Margin Deposit Liabilities Net investment income Allstate Protection and Run-off Property-Liability 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 Schedule of Amortized Cost, Gross Unrealized Gains (Losses) and Fair Value for Fixed Income Securities Debt Securities, Available-for-Sale [Table Text Block] Schedule of Fair Value of Instruments with Credit-Risk-Contingent Features Schedule of Derivative Instruments Credit Features in Liability Position and Netting [Table Text Block] Schedule of fair value of derivative instruments with termination, cross-default or collateral credit-risk-contingent features that are in a liability position and the fair value of assets and collateral that are netted against the liability. Schedule of Unrealized Net Capital Gains and Losses Included in AOCI Schedule of Unrealized Capital Gains and Losses Included in Accumulated Other Comprehensive Income [Table Text Block] This item represents the schedule of unrealized net capital gains and losses recorded in accumulated other comprehensive income by type of securities. Fixed Income Securities Valued Based on Nonbinding Broker Quotes Fixed Income Securities Valued Based on Nonbinding Broker Quotes [Member] Represents the fixed income securities valued based on non-binding broker quotes. Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Table] Liability for Unpaid Claim and Claim Adjustment Expense, Change [Table] 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 Contingent consideration Contingent Consideration Derivative [Member] Contingent Consideration Derivative Entity Address, State or Province Entity Address, State or Province Equity securities Payments to Acquire Equity Securities, FV-NI PEO Total Compensation Amount PEO Total Compensation Amount Gross Unrealized Gains Gross Unrealized Gains [Abstract] Unrealized foreign currency translation adjustments Change in unrealized foreign currency translation adjustments Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Assets Assets, Fair Value Disclosure [Abstract] Unrealized net capital gains and losses Change in unrealized net capital gains and losses Change in unrealized net capital gains and losses, after-tax Other Comprehensive Income (Loss), Available for Sale Securities, Including Other than Temporary Impairment Losses Adjustment Net of Tax Net of tax amount of the appreciation (loss) in the value of unsold available-for-sale securities. Includes amounts related to other than temporary impairment (OTTI) losses. Total derivatives, notional amount Notional amount Derivative, Notional Amount Weighted average common shares - Basic (in shares) Weighted average common shares outstanding (in shares) Weighted Average Number of Shares Outstanding, Basic Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Exposure, net of collateral Credit Derivative Exposure Net of Collateral The amount of credit exposure by counterparties net of collateral received, related to derivative contracts. Deferred policy acquisition costs Increase (Decrease) in Deferred Policy Acquisition Costs 2021 and prior Acquisition, 2021 and Prior [Member] Acquisition, 2021 and Prior Credit losses Total Allowance For Credit Loss, Credit Loss Recognized In Net Income Allowance For Credit Loss, Credit Loss Recognized In Net Income Investments Investments [Abstract] Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] Property and casualty Property And Casualty [Member] Property And Casualty Short-Duration Insurance Contract, Accident Year 2023 And 2024 Short-Duration Insurance Contract, Accident Year 2023 And 2024 [Member] Short-Duration Insurance Contract, Accident Year 2023 And 2024 Document Information [Line Items] Document Information [Line Items] Award Timing MNPI Disclosure Award Timing MNPI Disclosure [Text Block] Schedule of Rollforward of Level 3 Assets and Liabilities Held at Fair Value Schedule of Fair Value Assets and Liabilities Measured on Recurring Basis Unobservable Input Reconciliation [Table Text Block] This element represents, for the fair value measurement of assets and liabilities using significant unobservable inputs (Level 3), a reconciliation of the beginning and ending balances, separately presenting changes during the period attributable to the following: (1) total gains or losses for the period (realized and unrealized), segregating those gains or losses included in earnings (or changes in net assets), and a description of where those gains or losses included in earnings (or changes in net assets) are reported in the statement of income (or activities); (2) purchases, sales, issuances, and settlements (net); and (3) transfers in and transfers out of Level 3 (for example, transfers due to changes in the observability of significant inputs). Basis of presentation Basis of Accounting, Policy [Policy Text Block] Dividends paid on preferred stock Payments of Ordinary Dividends, Preferred Stock and Preference Stock Class of Stock [Axis] Class of Stock [Axis] 5.100% Fixed-to-Floating Rate Subordinated Debentures due 2053 Subordinated Debentures Due 2053 at 5.10 Percent [Member] Represents the subordinated debentures due in 2053 at an interest rate of 5.10 percent. Net income applicable to common shareholders, basic Net Income (Loss) Available to Common Stockholders, Basic Other investments Other than Securities Investment [Member] Credit exposure Counterparty Credit Exposure The amount of credit exposure by counterparties related to derivative contracts. Brokered solutions and collateral protection Brokered Solutions And Collateral Protection [Member] Brokered Solutions And Collateral Protection Change in Unrealized Gain (Loss) Recognized in Accumulated Other Comprehensive Income (Loss) Change in Unrealized Gain (Loss) Recognized in Accumulated Other Comprehensive Income (Loss) [Line Items] Deferred income taxes Deferred Income Taxes Recognized in Accumulated Other Comprehensive Income Accumulated adjustment to deferred income taxes related to unrealized capital gains and losses, as of the balance sheet date. Total mortgage loans Financing Receivable, Excluding Accrued Interest, after Allowance for Credit Loss Investment expense Investment Income, Investment Expense Earnings per common share Earnings Per Share, Policy [Policy Text Block] Adopted accounting standard and Pending accounting standard New Accounting Pronouncements, Policy [Policy Text Block] Noncontrolling interest Noncontrolling Interest [Member] Schedule of Reportable Segments Financial Performance Schedule of Business Segments Net Income (Loss) Disclosure [Table Text Block] The schedule of net income (loss) by segment. Other comprehensive income (loss) Other Comprehensive Income (Loss), before Tax Schedule of Portfolio Composition Summary Investment Holdings [Table Text Block] Debt Long-Term Debt Short-Duration Insurance Contracts, Accident Year [Domain] Short-Duration Insurance Contracts, Accident Year [Domain] Pledged by the Company Securities Pledged as Collateral to Counterparties This element represents securities pledged to counterparties as collateral for credit exposure. Other assets Other Security Investments [Member] Changes in: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Increase (Decrease) in Operating Capital [Abstract] Net cash used in 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] Personal other auto coverages Personal Other Auto Coverages [Member] Personal Other Auto Coverages Security Exchange Name Security Exchange Name Activity in the reserve for property-liability insurance claims and claims expense: Liability for Unpaid Claims and Claims Adjustment Expense, Net [Roll Forward] Gains (losses) included in net income for Level 3 assets and liabilities: Fair Value Assets and Liabilities Measured on Recurring Basis Unobservable Inputs Gain (Loss) [Line Items] Transaction Market Method [Axis] Transaction Market Method [Axis] Shares reissued under equity incentive plans, net Proceeds, Issuance of Shares, Share-Based Payment Arrangement, Including Option Exercised, Net Proceeds, Issuance of Shares, Share-Based Payment Arrangement, Including Option Exercised, Net Total recurring basis liabilities Liabilities, Fair Value Disclosure 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] Name Outstanding Recovery, Individual Name Award Timing, How MNPI Considered Award Timing, How MNPI Considered [Text Block] Fixed income securities, credit loss allowance Debt Securities, Available-For-Sale, Allowance For Credit Loss, Unrealized Loss Position, Excluding Accrued Interest Debt Securities, Available-For-Sale, Allowance For Credit Loss, Unrealized Loss Position, Excluding Accrued Interest Securities collateral (received) pledged Derivative Liability, Subject to Master Netting Arrangement, Collateral, Right to Reclaim Security Not Offset 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] Investments [Table] Schedule of Investments [Table] Changes in unrealized net capital gains and losses reported in OCI OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment and Tax Limited partnership interests Payments to Acquire Interest in Subsidiaries and Affiliates Proceeds from disposition of operations, net of cash transferred Proceeds from Divestiture of Businesses, Net of Cash Divested Other investments Payments to Acquire Other Investments Unrealized net capital gains and losses, pre-tax Total Unrealized Gains (Losses) on Investments before Taxes The amount of unrealized gain (loss) before taxes on all investment securities, which are included in accumulated other comprehensive income (loss), as a result of fair value exceeding (under) its cost, as of the balance sheet date. Unamortized pension and other postretirement prior service credit Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] Residential Residential Mortgage [Member] Asset Class [Domain] Asset Class [Domain] Compensation Amount Outstanding Recovery Compensation Amount Individual: Individual [Axis] Weighted average common shares - Diluted (in shares) Weighted average common and dilutive potential common shares outstanding (in shares) Weighted Average Number of Shares Outstanding, Diluted Entity Emerging Growth Company Entity Emerging Growth Company Amortized cost before allowance Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss Underlying Security Market Price Change Underlying Security Market Price Change, Percent Derivative Financial Instruments Derivative Instruments and Hedging Activities Disclosure [Text Block] Underwriting income (loss) by segment Underwriting Gain (Loss) A measure that is not based on GAAP, which is calculated as premiums earned, less claims and claims expense ("losses"), amortization of deferred policy acquisition costs ("DAC"), operating costs and expenses and restructuring and related charges, as determined using GAAP. Liability derivatives gross liability Gross amount Derivative Liability, Subject to Master Netting Arrangement, before Offset Subtotal Available for sale Securities, Debt Maturities with Single Maturity Date Amortized Cost This item represents the total of all debt securities grouped by maturity dates excluding asset-backed securities, residential mortgage-backed securities and commercial mortgage-backed securities, at cost, net of adjustments made for accretion, amortization, other-than-temporary impairments, and hedging, if any, which are classified neither as held-to-maturity nor trading securities. Accrued investment income Accrued Investment Income Receivable Discount rate (as a percent) Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate Net increases related to credit losses Net increases related to credit losses Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Period Increase (Decrease) Treasury stock Treasury Stock, Common [Member] Paid and due from reinsurers and indemnitors Reinsurance Recoverable for Paid Claims and Claims Adjustments Debt Securities, Available-for-Sale [Line Items] Debt Securities, Available-for-Sale [Line Items] Noncash consideration, warrants Noncash or Part Noncash Acquisition, Noncash Financial or Equity Instrument Consideration, Warrants Noncash or Part Noncash Acquisition, Noncash Financial or Equity Instrument Consideration, Warrants Organization, Consolidation and Presentation of Financial Statements [Abstract] Commercial Commercial Loan [Member] Total asset derivatives, notional amount Derivative Asset, Notional Amount Noncatastrophic Event [Domain] Noncatastrophic Event [Domain] All Executive Categories All Executive Categories [Member] Pension Adjustments Service Cost Pension Adjustments Service Cost [Member] After-tax Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] Schedule of Components of Net Cost (Benefit) for Pension and Other Postretirement Plans Schedule of Net Benefit Costs [Table Text Block] Settlements Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements Schedule of Computation of Basic and Diluted Earnings Per Common Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] 2022 Acquisition, 2022 [Member] Acquisition, 2022 Reportable Segments Segment Reporting [Text Block] Fixed income securities Proceeds from Maturities, Prepayments and Calls of Debt Securities, Available-for-Sale Minimum Minimum [Member] Total Investments, Fair Value Disclosure Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Variable Interest Entities Variable Interest Entity Disclosure [Text Block] Liabilities Liabilities Liabilities [Abstract] Income Statement Location [Axis] Location, Statement of Income, Balance [Axis] Non-Rule 10b5-1 Arrangement Adopted Non-Rule 10b5-1 Arrangement Adopted [Flag] Limited partnership interests Limited partnership interests carried at fair value 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] Fair Value Assets Measured on Recurring Basis Unobservable Input Reconciliation Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Derivatives Derivative [Member] Other liabilities Other Liabilities 2023 Acquisition, 2023 [Member] Acquisition, 2023 Total net (benefit) cost Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Common stock, shares authorized (in shares) Common Stock, Shares Authorized Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] Gross realized gains Debt Securities, Available-for-Sale, Realized Gain Exercise Price Award Exercise Price Schedule of Restructuring and Related Costs [Table] Restructuring Cost [Table] Exit costs Facility Closing [Member] Recurring basis Fair Value, Recurring [Member] Fixed income securities, unrealized losses Debt Securities, Available-for-Sale, Unrealized Loss Segment Reporting Segment Reporting [Line Items] Document Quarterly Report Document Quarterly Report 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] Municipal US States and Political Subdivisions Debt Securities [Member] Income taxes Increase (Decrease) in Income Taxes Payable, Net of Income Taxes Receivable Fixed income securities Proceeds from Sale of Debt Securities, Available-for-Sale Prior years Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Prior Years Commitments to fund line of credit, commercial mortgage loans and bank loans Unfunded Loan Commitments Unfunded Loan Commitments Liability derivatives Derivative Liability [Abstract] Awards Close in Time to MNPI Disclosures, Table Awards Close in Time to MNPI Disclosures [Table Text Block] Equity Method Investments Equity Method Investments Restructuring liability, beginning balance Restructuring liability, ending balance Restructuring Reserve Equity Component [Domain] Equity Component [Domain] Total gains (losses) included in: Net income Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings Foreign currency contracts Foreign Exchange Contract [Member] Costs and expenses Benefits, Losses and Expenses [Abstract] Adoption Date Trading Arrangement Adoption Date Restructuring Type [Axis] Restructuring Type [Axis] Equity securities, at fair value (cost $10,071 and $8,026) Equity securities, at fair value Equity securities Equity Securities, FV-NI, Current Title Trading Arrangement, Individual Title Forgone Recovery due to Disqualification of Tax Benefits, Amount Forgone Recovery due to Disqualification of Tax Benefits, Amount Other investments Payments For (Proceeds From) Other Investments Payments For (Proceeds From) Other Investments Restatement does not require Recovery Restatement Does Not Require Recovery [Text Block] Other Proceeds from (Payment for) Other Financing Activity Insider Trading Policies and Procedures Adopted Insider Trading Policies and Procedures Adopted [Flag] Accident and health insurance Allstate Accident And Health [Member] Allstate Accident And Health Net gains (losses) on investments and derivatives Net gains (losses) on investments and derivatives Realized Capital Gains (Losses), Continuing Operations Realized Capital Gains (Losses), Continuing Operations Commercial Commercial Portfolio Segment [Member] Derivative Instruments, Gain (Loss) Derivative Instruments, Gain (Loss) [Line Items] Protection and insurance products Protection And Insurance Products [Member] Finance And Insurance Products [Member] Current year Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid, Current Year Type of Restructuring [Domain] Type of Restructuring [Domain] Compensation Actually Paid vs. Net Income Compensation Actually Paid vs. Net Income [Text Block] Financial Asset, Aging [Domain] Financial Asset, Aging [Domain] Common stock, $.01 par value, 2.0 billion shares authorized and 900 million issued, 254 million and 260 million shares outstanding Common Stock, Value, Outstanding Remeasurement of benefit obligation (gains) losses: Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] All Adjustments to Compensation All Adjustments to Compensation [Member] All other Segment Reporting, Reconciling Item, Corporate Nonsegment [Member] Net cash provided by operating activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation Preferred stock, value aggregate liquidation preference Preferred Stock, Liquidation Preference, Value Residential Residential Portfolio Segment [Member] Prior year reserve reestimates excluding catastrophes Prior years Prior Year Claims and Claims Adjustment Expense Income Statement [Abstract] Income Statement [Abstract] Adjusted net income (loss) by segment, after-tax Operating Income (Loss) after Tax The operating income (loss), net of tax effect, as measured by the entity for segment reporting purposes. Document Transition Report Document Transition Report Limited partnerships Noncontrolling Interest in Limited Partnerships Other investments Proceeds from Maturities, Prepayments and Calls of Other Investments Favorable Severity Development Favorable Severity Development [Member] Favorable Severity Development Net (increases) decreases related to credit losses previously reported Debt Securities, Available-for-Sale, Excluding Accrued Interest, Allowance for Credit Loss, Previously Recorded Debt Securities, Available-for-Sale, Excluding Accrued Interest, Allowance for Credit Loss, Previously Recorded Discount rate for reserve for future policy benefits Accumulated Future Policy Benefit Adjustment, Discount Rate, Parent [Member] Accumulated Future Policy Benefit Adjustment, Discount Rate, Parent Intersegment eliminations Intersegment Eliminations [Member] Stock Appreciation Rights (SARs) Stock Appreciation Rights (SARs) [Member] Increase (decrease) in claims and claims expense Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] City Area Code City Area Code Non-cash financing activities related to the issuance of shares for vested restricted stock units Stock Issued During Period, Value, Conversion of Units Short-Duration Insurance Contracts, Accident Year [Axis] Short-Duration Insurance Contracts, Accident Year [Axis] Document Information [Table] Document Information [Table] Name Forgone Recovery, Individual Name Non-GAAP Measure Description Non-GAAP Measure Description [Text Block] Property-liability insurance claims and claims expense Liability for Unpaid Claims and Claims Adjustment Expense [Line Items] Preferred stock, shares issued (in shares) Preferred Stock, Shares Issued Amortization of prior service credit Defined Benefit Plan, Amortization of Prior Service Cost (Credit) Investment income, before expense Interest and Dividend Income, Operating Change in short-term and other investments, net Payments for (Proceeds from) Short-Term Investments Unrealized net holding gains and losses arising during the period, net of related offsets Other Comprehensive Income (Loss), before Reclassifications, before Tax NEW YORK STOCK EXCHANGE, INC. NEW YORK STOCK EXCHANGE, INC. [Member] Number of  issues Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions Asset derivatives, gross liability Counter-party netting Derivative Asset, Subject to Master Netting Arrangement, Liability Offset Measurement Basis [Axis] Measurement Basis [Axis] Total investments Investments Investments Total Level 3 gains (losses) included in net income Fair Value, Assets and Liabilities Measured on Recurring Basis, Gain (Loss) Included in Earnings [Abstract] Unrealized net capital gains and losses AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-Sale, Parent [Member] Erroneously Awarded Compensation Recovery Erroneously Awarded Compensation Recovery [Table] Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Table] Entity Current Reporting Status Entity Current Reporting Status Schedule of Gross Realized Gains (Losses) on Sales of Fixed Income Securities Schedule Of Gross Realized Gains (Losses) On Sales Of Fixed Income Securities [Table Text Block] Schedule Of Gross Realized Gains (Losses) On Sales Of Fixed Income Securities [Table Text Block] Net cash used in financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation Total Shareholder Return Amount Total Shareholder Return Amount Liabilities Liabilities, Fair Value Disclosure [Abstract] Gain (loss) included in earnings Fair Value, Assets and Liabilities Measured on Recurring Basis, Gain (Loss) Included in Earnings Unrealized foreign currency translation adjustments Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax Discount rate for reserve for future policy benefits Change in discount rate for reserve for future policy benefits OCI, Liability for Future Policy Benefit, Gain (Loss), after Reclassification Adjustment and Tax Claims and claims expense and other insurance reserves Increase (Decrease) in Future Policy Benefit Reserves and Other Insurance Liabilities Adjustments to reconcile net income to net cash provided by operating activities: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract] Guarantees and Contingent Liabilities Commitments Contingencies and Guarantees [Text Block] Cash flows from financing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract] Property and equipment, net Property, Plant, and Equipment, after Accumulated Depreciation, Depletion, and Amortization Interest cost Defined Benefit Plan, Interest Cost Net Investment Income: Net Investment Income [Line Items] Financial Instruments [Domain] Financial Instruments [Domain] Tax Other Comprehensive Income (Loss), Tax [Abstract] Net amount on balance sheet Net amount on balance sheet Derivative Asset Other revenue Other Income Gross Unrealized Losses Gross Unrealized Loss [Abstract] Underlying Securities Award Underlying Securities Amount Less: Comprehensive (loss) income attributable to noncontrolling interest Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Fair value Estimate of Fair Value Measurement [Member] Total unrealized losses Total Unrealized Loss [Abstract] Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Net change in proceeds managed Net Change In Proceeds Managed Collateral The net change in the proceeds managed related to collateral received in conjunction with the entity's securities lending and over-the-counter derivatives. Auto Auto [Member] Represents total auto coverage. Cash Cash Write-offs Debt Securities, Available-for-Sale, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff Subsegments [Axis] Subsegments [Axis] Preferred stock par value Preferred Stock [Member] Schedule of Gain (Loss) on Securities [Table] Schedule of Gain (Loss) on Securities [Table] Change in unrealized net capital gains and losses OCI, Debt Securities, Available-for-Sale, Gain (Loss), after Adjustment, before Tax Segment Reporting [Table] Segment Reporting [Table] Total derivatives, Number of contracts Derivative, Number of Instruments Held Realized capital gains and losses by asset type Other than Temporary Impairment Losses by Asset Type [Line Items] Other than Temporary Impairment Losses by Asset Type All Trading Arrangements All Trading Arrangements [Member] Balance at the beginning of the period Balance at the end of the period Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value Fair value Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, Less than 12 Months Schedule of Assets and Liabilities Measured at Fair Value Fair Value Measurements, Recurring and Nonrecurring [Table Text Block] Other Performance Measure, Amount Other Performance Measure, Amount Award Timing MNPI Considered Award Timing MNPI Considered [Flag] Current Fiscal Year End Date Current Fiscal Year End Date Non-PEO NEO Average Total Compensation Amount Non-PEO NEO Average Total Compensation Amount Derivative [Line Items] Derivative [Line Items] NAIC 4 / B Standard & Poor's, B Rating [Member] NAIC 1 / A A Standard & Poor's, A Rating [Member] Restructuring Reserve [Roll Forward] Restructuring Reserve [Roll Forward] 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] 2024 Acquisition 2024 [Member] Acquisition 2024 Dividends on common stock (in dollars per share) Common Stock, Dividends, Per Share, Declared Entity File Number Entity File Number Series I Preferred Stock Series I Preferred Stock [Member] Series I Preferred Stock Net change in proceeds managed Net Change in Proceeds Managed [Abstract] Due in one year or less Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Fair Value Shares reissued under equity incentive plans, net Shares Issued, Value, Share-Based Payment Arrangement, after Forfeiture Unrealized net capital gains and losses Unrealized net capital gains and losses, after-tax AOCI, Debt Securities, Available-for-Sale, Adjustment, after Tax Schedule of Maturities for Fixed Income Securities Investments Classified by Contractual Maturity Date [Table Text Block] Schedule of Rollforward of the Reserve for Property and Casualty Insurance Claims and Claims Expense and Prior Year Reserve Re-Estimates Included in Claims and Claims Expense Schedule of Liability for Unpaid Claims and Claims Adjustment Expense [Table Text Block] Recovery of Erroneously Awarded Compensation Disclosure [Line Items] Measure: Measure [Axis] Schedule of Assets and Liabilities of Reciprocal Exchanges Schedule of Variable Interest Entities [Table Text Block] Guarantees and Contingent Liabilities Guarantees and Contingent Liabilities Credit Derivatives Contract Type [Domain] Credit Derivatives Contract Type [Domain] Treasury stock, shares (in shares) Treasury Stock, Common, Shares Insurance premiums and contract charges Insurance premiums Premiums Earned, Net Equity Components [Axis] Equity Components [Axis] Operating costs and expenses Other Cost and Expense, Operating Schedule of Credit Losses Recognized in Net Income Allowance For Credit Loss, Credit Losses Recognized In Earnings [Table Text Block] Allowance For Credit Loss, Credit Losses Recognized In Earnings Fair value Fair Value Securities [Abstract] Schedule of Credit Derivatives [Table] Credit Derivative [Table] Entity Interactive Data Current Entity Interactive Data Current Reinsurance Effects of Reinsurance [Line Items] Other liabilities Other Liability Class [Member] Other Liability Class Run-off Property-Liability Run-Off Property-Liability [Member] Run-Off Property-Liability Less: Net income (loss) attributable to noncontrolling interest Net Income (Loss) Attributable to Noncontrolling Interest Entity Small Business Entity Small Business Fixed income securities Available for sale Fixed Income Securities, Unrealized Loss Included in Other Comprehensive Income Represents the unrealized losses included in accumulated other comprehensive income as of the balance sheet date, for the fixed income securities which are categorized neither as held-to-maturity nor trading securities. Unearned premiums Unearned Premiums Comprehensive income attributable to Allstate Comprehensive Income (Loss), Net of Tax, Attributable to Parent Schedule of Valuation Changes Included in Net Income and OCI for Level 3 Assets and Liabilities Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Table Text Block] Group health Group Health [Member] Represents accident, health and other coverage. Settlements Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements Private equity Private Equity [Member] Private Equity [Member] MNPI Disclosure Timed for Compensation Value MNPI Disclosure Timed for Compensation Value [Flag] Earnings per common share: Earnings Per Share, Attributable to Parent [Abstract] Schedule of Net Gains (Losses) on Investments and Derivatives by Asset Type Schedule of Gain (Loss) on Investments by Security Type [Table Text Block] This item represents the schedule of realized gains and losses reported in the statement of income by type of securities. Document Type Document Type Fair value of assets and liabilities measured on recurring and non-recurring basis Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Employer voluntary benefits Employer Voluntary Benefits [Member] Employer Voluntary Benefits Beginning balance Ending balance Debt Securities, Available-for-Sale, Allowance for Credit Loss, Excluding Accrued Interest Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Debt Securities, Trading, and Equity Securities, FV-NI [Table] Debt Securities, Trading, and Equity Securities, FV-NI [Table] Local Phone Number Local Phone Number Postretirement benefits Other Postretirement Benefits Plan [Member] Short-term, at fair value (amortized cost $4,874 and $4,888) Short-term investments, at fair value Short-term investments Other Short-Term Investments Fair Value, Asset (Liability), Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Fair Value, Asset (Liability), Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Commitments and Contingent Liabilities (Note 11) Commitments and Contingencies Changed Peer Group, Footnote Changed Peer Group, Footnote [Text Block] Realized capital gains and losses by asset type Gain (Loss) on Securities [Line Items] External Credit Rating, Standard & Poor's [Domain] External Credit Rating, Standard & Poor's [Domain] Executive Category: Executive Category [Axis] Other comprehensive income (loss) Other Comprehensive Income (Loss), Tax Reinsurance and Indemnification Reinsurance [Text Block] Corporate - privately placed Corporate Debt Securities, Private Placement [Member] Corporate Debt Securities, Private Placement [Member] Non-PEO NEO Average Compensation Actually Paid Amount Non-PEO NEO Average Compensation Actually Paid Amount Schedule of Variable Interest Entities [Table] Variable Interest Entity [Table] Supplemental Cash Flow Information [Abstract] Supplemental Cash Flow Information [Abstract] PEO Name PEO Name Total paid Liability for Unpaid Claims and Claims Adjustment Expense, Claims Paid Other liabilities and expenses Accrued Liabilities and Other Liabilities Limited partnership interests Proceeds From Divestiture Of Interest In Limited Partnership Interest Proceeds From Divestiture Of Interest In Limited Partnership Interest Financial liabilities Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract] All other Segment Reporting, Other Segment Item, Amount Pension and other postretirement remeasurement (gains) losses Pension and other postretirement remeasurement gains (losses) Remeasurement (gains) losses Remeasurement (gains) losses Defined Benefit Plan, Actuarial Gain (Loss), Immediate Recognition as Component in Net Periodic Benefit (Cost) Credit AAA Standard & Poor's, AAA Rating [Member] Stock Price or TSR Estimation Method Stock Price or TSR Estimation Method [Text Block] Entity Tax Identification Number Entity Tax Identification Number Amortized cost, net Debt Securities, Available-for-Sale, Amortized Cost, Rolling Maturity [Abstract] Schedule of Payment Status of Mortgage Loans Financing Receivable, Past Due [Table Text Block] Current before allowance Financial Asset, Not Past Due [Member] Less: Preferred stock dividends Preferred stock dividends Preferred Stock Dividends, Income Statement Impact Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Accident and health insurance premiums and contract charges Accident and Health Insurance Product Line [Member] Decrease (increase) in the provision for credit losses Reinsurance Recoverable, Allowance for Credit Loss, Period Increase (Decrease) Schedule of Exchange Traded and Cleared Margin Deposits Schedule Of Margin Deposits [Table Text Block] Schedule Of Margin Deposits Aggregate Erroneous Compensation Not Yet Determined Aggregate Erroneous Compensation Not Yet Determined [Text Block] Purchases Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases Material Terms of Trading Arrangement Material Terms of Trading Arrangement [Text Block] 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] Comprehensive income Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Measurement Frequency [Domain] Measurement Frequency [Domain] AA- Standard & Poor's, AA- Rating [Member] Discount rate for reserve for future policy benefits AOCI, Liability For Future Policy Benefit, Discount Rate, Before Tax AOCI, Liability For Future Policy Benefit, Discount Rate, Before Tax Liability for Unpaid Claims and Claims Adjustment Expense [Table] Liability for Unpaid Claims and Claims Adjustment Expense [Table] Schedule of the activity in the reserve for settling insured claims and expenses incurred in the claims settlement process for the period. Short-term investments Available For Sale Short-Term Investments, Unrealized Gain (Loss) Included In Other Comprehensive Income Available For Sale Short-Term Investments, Unrealized Gain (Loss) Included In Other Comprehensive Income Schedule of Volume and Fair Value Positions of Derivative Instruments Schedule of Derivative Instruments in Statement of Financial Position, Fair Value [Table Text Block] Net income applicable to common shareholders per common share - Basic (in dollars per share) Earnings per common share - Basic (in dollars per share) Earnings Per Share, Basic Insider Trading Arrangements [Line Items] Changes in: Changes in [Abstract] Amortization of deferred policy acquisition costs Amortization of DAC Amortization of DAC Deferred Policy Acquisition Costs, Amortization Expense 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] Gain on disposition of operations Gain on disposition of operations Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal Fair Value Measurement [Domain] Fair Value Measurement [Domain] Cash collateral (received) pledged Derivative Asset, Subject To Master Netting Arrangement, Collateral, Obligation To Return Cash, Offset Against Derivative Asset, Net Derivative Asset, Subject To Master Netting Arrangement, Collateral, Obligation To Return Cash, Offset Against Derivative Asset, Net Compensation Actually Paid vs. Company Selected Measure Compensation Actually Paid vs. Company Selected Measure [Text Block] Cover [Abstract] Cover [Abstract] Investment assets, useful life (in years) Investment Assets, Useful Life Investment Assets, Useful Life Reinsurance Recoverable, Allowance for Credit Loss [Roll Forward] Reinsurance Recoverable, Allowance for Credit Loss [Roll Forward] Equity Awards Adjustments Equity Awards Adjustments [Member] Commercial lines Commercial lines Property and Casualty, Commercial Insurance [Member] Fair Value Balance Sheet Grouping Financial Statement Captions Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Schedule of Gains (Losses) from Valuation and Settlements Reported on Derivatives Schedule of Derivative Instruments Gain (Loss) in Statement of Financial Performance Valuation Settlements Hedge Ineffectiveness Fair Value Hedges and Not Designated Hedges [Table Text Block] Schedule of gains and losses from valuation, settlements, and hedge ineffectiveness reported on derivatives used in fair value hedging relationships and derivatives not designated as accounting hedging instruments in the statement of operations. Schedule of Mortgage Loans, Net of Credit Allowance Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block] Premium installment receivables, net Increase (Decrease) in Premiums Receivable Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration] Short-term investments Short-Term Investments [Member] Fixed income securities Available for sale Fixed Income Securities, Unrealized Gain Included in Other Comprehensive Income Represents the unrealized gains included in accumulated other comprehensive income as of the balance sheet date, for the fixed income securities which are categorized neither as held-to-maturity nor trading securities. Reserve for Property and Casualty Insurance Claims and Claims Expense Reserve for Property Liability Insurance Claims and Claims Expense Disclosure [Text Block] Describes the various components of the reserve for property-liability future policy benefits and guaranteed minimum benefits, and for claims and claims adjustment expenses; the significant assumptions for estimating claims losses; causes of significant variances from prior periods (such as catastrophes, asbestos and environmental claims reserve losses); and reconciliations of beginning to ending reserve balances. Equity Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Schedule of Rollforward of Credit Loss Allowance for Reinsurance Recoverables Reinsurance Recoverable, Allowance for Credit Loss [Table Text Block] Preferred stock, shares authorized (in shares) Preferred Stock, Shares Authorized Derivatives, Fair Value Derivatives, Fair Value [Line Items] Stock options (in shares) Incremental Common Shares Attributable to Employee Stock Options Aggregate awards of share options to be issued to an employee under a share-based compensation arrangement considered for purposes of computing diluted earnings per share. Investment collections Proceeds from Collection of Investments [Abstract] Hedging Designation [Domain] Hedging Designation [Domain] Preferred stock additional capital paid-in Preferred Stock Including Additional Paid in Capital [Member] Class of Stock [Domain] Class of Stock [Domain] Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Sales Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Sales Aggregate Available Trading Arrangement, Securities Aggregate Available Amount Contingent consideration term (in years) Disposal Group, Including Discontinued Operation, Contingent Consideration, Term Disposal Group, Including Discontinued Operation, Contingent Consideration, Term Counterparty and cash collateral netting Derivative Asset Net of Offsets and Securities Collateral Represents the amount of derivative assets, net of offsets under the master netting arrangements and net of securities collateral. Schedule of Gross and Net Amounts for OTC Derivatives Offsetting Assets and Liabilities [Table Text Block] Tabular disclosure of derivative and other financial assets and liabilities that are subject to offsetting, including master netting arrangements. Pay vs Performance Disclosure Pay vs Performance Disclosure [Table] Derivative instruments Fair Value of Derivative Instruments with Unrealized Net Capital Gain (Loss) Fair value as of the balance sheet date of the net amount of all assets and liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments, for which an unrealized net gain or loss is included in accumulated other comprehensive income. Retirement Plan Type [Domain] Retirement Plan Type [Domain] Entity Filer Category Entity Filer Category Due in one year or less Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Rolling within One Year, Amortized Cost Advertising expense Advertising Expense Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward] Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward] Valuation change and settlements of derivatives Gain (Loss) on Derivative Instruments, Net, Pretax Contractholder fund deposits Additions to Contract Holders Funds Financial Asset, Aging [Axis] Financial Asset, Aging [Axis] Derivatives not designated as accounting hedging instruments Not Designated as Hedging Instrument [Member] Total included in net income Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss) Allowance Allowance for Loan and Lease Losses, Real Estate Net income Net income Net income (loss) Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Interest rate cap agreements Interest Rate Cap [Member] Net amount on balance sheet Net amount on balance sheet Derivative Liability General General [Text Block] The disclosure of both the organization, consolidation and presentation of financial statements and the disclosure of the new accounting pronouncements adopted and not yet adopted. Entity Address, Address Line One Entity Address, Address Line One Right-of-use asset obtained in exchange for operating lease liability Right-of-Use Asset Obtained in Exchange for Operating Lease Liability Total costs and expenses Benefits, Losses and Expenses Income tax expense Income Tax Expense (Benefit) Income Tax Expense (Benefit) Series H Preferred Stock Series H Preferred Stock [Member] Derivative instruments Derivative Instruments, Unrealized Gain (Loss) Included in Other Comprehensive Income The amount of unrealized gains (losses) included in accumulated other comprehensive income on derivative instruments, as a result of fair value exceeding (under) its amortized cost, as of the balance sheet date. Bank loans Bank loans, net Bank Loans [Member] Bank Loans [Member] Write-offs Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff Premium installment receivables, net Premiums Receivable, Net Other investments Other Investment Assets [Member] Other Investment Assets Variable Interest Entity, Primary Beneficiary Variable Interest Entity, Primary Beneficiary [Member] Allstate Protection Total Allstate Protection insurance premiums Allstate Protection [Member] Allstate Protection comprises two brands, the Allstate brand and Encompass brand. Debt securities valued based on third-party discounted cash flow pricing models Debt Securities, Available-for-Sale, Excluding Accrued Interest, Third-Party Discounted Cash Flow Models Debt Securities, Available-for-Sale, Excluding Accrued Interest, Third-Party Discounted Cash Flow Models Statement [Table] Statement [Table] Personal auto injury coverage Personal Auto Injury Coverage [Member] Personal Auto Injury Coverage Catastrophic Event [Axis] Catastrophic Event [Axis] All other Segment Reporting, Reconciling Item, Excluding Corporate Nonsegment [Member] Credit Rating, Standard & Poor's [Axis] Credit Rating, Standard & Poor's [Axis] Asset derivatives, gross asset Gross amount Derivative Asset, Subject to Master Netting Arrangement, before Offset Net change in short-term investments Net Change in Short Term Investments of Proceeds Managed Collateral The net change in short-term investments from the proceeds managed related to collateral received in conjunction with the entity's securities lending and over-the-counter derivatives. Notional amount Notional Amount of Counterparty Credit Exposure The notional amount of derivative contracts for which the entity has counterparty credit exposure. Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative Instruments and Hedging Activities Disclosure [Abstract]