Summary of Significant Accounting Policies (Policies)	9 Months Ended
Summary of Significant Accounting Policies (Policies)	Sep. 30, 2023
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation These unaudited condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States ("GAAP") and Article 10 of Regulation S-X, for interim financial information. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In addition, the year-end balance sheet data was derived from audited financial statements but does not include all disclosures required by GAAP. In the opinion of management, these unaudited condensed consolidated financial statements reflect all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation of the Company's financial position and results of operations as at the end of, and for, the periods presented.
Basis of Presentation	These financial statements include the accounts of Hamilton Group, Hamilton Re, Hamilton U.K. Holdings Limited, Hamilton Select, HMGA Americas, ACML, and TS Hamilton Fund (collectively the "Company"). All significant intercompany transactions and balances have been eliminated on consolidation. Certain comparative information has been reclassified to conform to the current year presentation.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported and disclosed amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. The major estimates recorded in the Company’s financial statements include, but are not limited to, premiums written, provisions for estimated future credit losses, the reserve for losses and loss adjustment expenses and the fair value of investments.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Recently Adopted Accounting Pronouncements In February 2016, the FASB issued ASU 2016-02 Leases (as subsequently clarified in various Updates) which updated accounting guidance that applies to any entity that enters into a lease that does not meet certain scope exceptions. The guidance requires the recognition of lease assets and lease liabilities by lessees for those leases classified as operating leases under previous guidance. The Company adopted this guidance in the first quarter of 2022 by recording a gross-up of the balance sheet in recognition of an operating lease liability for future lease payments and the associated right-of-use asset for the right to use the underlying asset over the lease term. This guidance did not have a material impact on the Company’s results of operations, financial position, cash flows or disclosures. In June 2016, the FASB issued ASU 2016-13 Measurement of Credit Losses on Financial Instruments (as subsequently clarified in various Updates), which requires the application of an incurred loss impairment methodology that reflects expected credit losses and requires consideration of a broad range of reasonable and supportable information to record credit loss estimates. The Company adopted this guidance in the first quarter of 2022, and because it did not have a material impact on the Company’s results of operations, financial position, or cash flows, we did not record a cumulative effective adjustment to opening retained earnings as of January 1, 2022.