General (Policies)	9 Months Ended
General (Policies)	Sep. 30, 2022
General [Abstract]
Basis of presentation	Basis of presentation The accompanying condensed consolidated financial statements include the accounts of The Allstate Corporation (the “Corporation”) and its wholly owned subsidiaries, primarily Allstate Insurance Company (“AIC”), a property and casualty insurance company with various property and casualty and investment subsidiaries (collectively referred to as the “Company” or “Allstate”) and variable interest entities (“VIEs”) in which the Company is considered a primary beneficiary. These condensed consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). The condensed consolidated financial statements and notes as of September 30, 2022 and for the three and nine month periods ended September 30, 2022 and 2021 are unaudited. The condensed consolidated financial statements reflect all adjustments (consisting only of normal recurring accruals) which are, in the opinion of management, necessary for the fair presentation of the financial position, results of operations and cash flows for the interim periods. These condensed consolidated financial statements and notes should be read in conjunction with the consolidated financial statements and notes thereto included in the Company’s annual report on Form 10-K for the year ended December 31, 2021. The results of operations for the interim periods should not be considered indicative of results to be expected for the full year. All significant intercompany accounts and transactions have been eliminated.
Pending accounting standard	Pending accounting standard Accounting for Long-Duration Insurance Contracts In August 2018, the Financial Accounting Standards Board (”FASB”) issued guidance revising the accounting for certain long-duration insurance contracts. As disclosed in Note 3, the Company sold substantially all of its life and annuity business in scope of the new standard. The Company’s reserves and deferred policy acquisition costs (“DAC”) for certain voluntary and individual life and accident and health insurance products are subject to the new guidance. Under the new guidance, measurement assumptions, including those for mortality, morbidity and policy terminations, will be required to be reviewed at least annually, and updated as appropriate. The effects of updating assumptions other than the discount rate are required to be measured on a retrospective basis and reported in net income. In addition, reserves under the new guidance are required to be discounted using an upper-medium grade fixed income instrument yield that is updated through other comprehensive income (“OCI”) at each reporting date. Current GAAP requires the measurement of reserves to utilize assumptions set at policy issuance unless updated current assumptions indicate that recorded reserves are deficient. The new guidance also requires DAC and other capitalized balances currently amortized in proportion to premiums or gross profits to be amortized on a constant level basis over the expected term for all long-duration insurance contracts. DAC will not be subject to loss recognition testing but will be reduced when actual lapse experience exceeds expected experience. The new guidance is effective for financial statements issued for reporting periods beginning after December 15, 2022 and restatement of prior periods presented is required. The new guidance will be applied to affected contracts and DAC on the basis of existing carrying amounts at the earliest period presented. In July 2022, the FASB issued an Exposure Draft of an Accounting Standards Update (“Exposure Draft”) that would provide reporting entities with an accounting policy election to not apply the new guidance to insurance contracts in-force on the January 1, 2021 transition date but sold prior to the January 1, 2023 effective date provided certain conditions are met. The Company will adopt the new guidance effective January 1, 2023, using the modified retrospective approach and make the accounting policy election to not apply the new guidance to insurance contracts in-force on the transition date but sold prior to the effective date. The total impact on equity of implementing the new guidance is expected to be a decrease of between $250 million and $350 million. The expected decrease in equity includes the anticipated decrease in AOCI of between $235 million and $315 million primarily attributable to a change in the discount rate used in measuring the liability for future policy benefits for traditional life contracts and other long-term products with guaranteed terms from a portfolio-based rate at contract issuance to an upper-medium grade fixed income-based rate. The expected decrease in equity also includes the anticipated decrease in retained income of between $15 million and $35 million which primarily relates to certain long-term contracts with guaranteed terms with net premium ratios that are required to be adjusted at the transition date. The impact on equity, AOCI, and retained income excludes sold contracts that would meet the conditions included in the Exposure Draft. The estimated impact to AOCI at transition date is expected to decline significantly at the effective date due to the increase in the discount rate between the transition date and effective date.
Earnings per common share	Basic earnings per common share is computed using the weighted average number of common shares outstanding, including vested unissued participating restricted stock units. Diluted earnings per common share is computed using the weighted average number of common and dilutive potential common shares outstanding. For the Company, dilutive potential common shares consist of outstanding stock options, unvested non-participating restricted stock units and contingently issuable performance stock awards. The effect of dilutive potential common shares does not include the effect of options with an anti-dilutive effect on earnings per common share because their exercise prices exceed the average market price of Allstate common shares during the period or for which the unrecognized compensation cost would have an anti-dilutive effect.