Business and Significant Accounting Policies	3 Months Ended
Business and Significant Accounting Policies	Mar. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Business and Significant Accounting Policies	Business and Significant Accounting Policies The accompanying Condensed Consolidated Financial Statements of Argo Group International Holdings, Inc. and its subsidiaries (“Argo Group,” “we,” “us,” “our” or the “Company”) have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information and with the instructions for Form 10-Q and Article 10 of Regulation S-X. Argo Group is an underwriter of specialty insurance products in the property and casualty market. On November 16, 2023, we merged with Brookfield Reinsurance Ltd., which resulted in a change to the Company’s ownership, (the “Merger”). Brookfield Reinsurance Ltd. elected to push-down its purchase accounting, which resulted in the Company reflecting the fair market value of our assets and liabilities as of November 16, 2023, in accordance with Accounting Standards Codification (“ASC”) 805, Business Combinations. The application of push-down accounting created a new basis of accounting for all of our assets and liabilities. As such, the Company’s financial position, results of operations, and cash flows subsequent to the acquisition are not comparable with those prior to November 16, 2023, and therefore have been separated to indicate pre-acquisition and post-acquisition periods. The pre-acquisition period through November 15, 2023 is referred to as the Predecessor. The post-acquisition period, November 16, 2023 and forward, includes the impact of push-down accounting and is referred to as the Successor. The preparation of interim financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of revenues and expenses during the reporting period. The major estimates reflected in our Condensed Consolidated Financial Statements include, but are not limited to, reserves for losses and loss adjustment expenses; reinsurance recoverables, including the reinsurance recoverables allowance for expected credit losses; fair value of investments and assessment of potential impairment, including the allowance for credit losses on fixed maturity securities; valuation of intangibles, including those identified as part of purchase accounting related to the Merger, and our deferred tax asset valuation allowance. Actual results could materially differ from those estimates. Certain financial information that is normally included in annual Condensed Consolidated Financial Statements, including certain financial statement footnotes, prepared in accordance with GAAP, is not required for interim reporting purposes and has been condensed or omitted. These statements should be read in conjunction with the Condensed Consolidated Financial Statements and notes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2023 filed with the Securities and Exchange Commission ("SEC") (the “2023 Form 10-K”). The interim financial information as of, and for the three months ended, March 31, 2024 and 2023 is unaudited. However, in the opinion of management, the interim information includes all adjustments, consisting of normal recurring accruals, necessary for a fair presentation of the results presented for the interim periods. The operating results for the interim periods are not necessarily indicative of the results to be expected for the full year. All material intercompany amounts have been eliminated in consolidation. Certain reclassifications have been made to financial information presented for prior years to conform to the current year’s presentation. Sale of Argo Underwriting Agency Limited On September 8, 2022, Argo International Holdings Limited (the “Seller”), a wholly-owned subsidiary of the Company, and Ohio Farmers Insurance Company (the “Buyer”), part of the Westfield group of insurance companies, entered into a sale and purchase agreement (the “Transaction”) under which the Seller agreed to sell, and the Buyer agreed to purchase, the entire issued share capital of AUA, for which the financial results are reported in our International segment. This transaction simplifies our reporting structure and is intended to drive greater efficiencies. The base cash consideration for the purchase was $125.0 million, which was adjusted to reflect the extent by which AUA’s net assets as at completion are greater or lesser than AUA net assets as of March 31, 2022. In the third quarter of 2022, as a result of the sale, an impairment was recorded in the amount of $28.5 million, consisting of $17.3 million of indefinite lived intangible assets and $11.2 million of goodwill, representing the difference between the carrying value and implied fair value as determined by the consideration to be received. In addition, the Buyer replaced certain funds provided by the Company to support the activities of AUA and certain of its subsidiaries at Lloyd’s of London, which were subsequently released to the Company. As of December 31, 2022, the Company reported the assets and liabilities of this block of business as held-for-sale on Consolidated Balance Sheets with results continuing to be reported within the Consolidated Statements of Comprehensive Income (Loss) and the International Operations segment. The Company determined that the Transaction did not represent a strategic shift, and therefore, did not meet the requirements for discontinued operations. On February 2, 2023, the Seller completed the sale of the entire issued share capital of AUA. At the closing, the Company received total consideration of $155.7 million, which included cash proceeds of $125.1 million as base consideration and an additional $30.6 million which was placed in escrow by the Buyer related to certain reinsurance-related recoverables. The funds in escrow may be released to the Seller over a period of two years following the closing. At the end of the two-year escrow period, any remaining balance of the escrow will be returned to the Buyer. As a result of the sale, we realized a loss of $20.3 million in the first quarter of 2023, which is included as a component of Net realized investment and other gains (losses) in our Consolidated Statements of Comprehensive Income (Loss). This loss is due to the realization of unrealized investment losses, which was previously a component of accumulated other comprehensive income. The total consideration was adjusted to $161.3 million based on a mutually agreed final closing balance sheet, which resulted in an additional $5.6 million of cash proceeds received by the Company in July 2023. Since the sale of AUA, $12.9 million of the consideration placed in escrow was released to the Company.