SIGNIFICANT ACCOUNTING POLICIES (Policies)	9 Months Ended
Sep. 30, 2026
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation These unaudited condensed consolidated financial statements (the “financial statements”) have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) for interim financial information, and with the U.S. Securities and Exchange Commission’s (“SEC”) instructions to Quarterly Report on Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all the information and footnotes required by U.S. GAAP for complete financial statements. The financial statements should be read in conjunction with the Company’s audited consolidated financial statements included in the Company’s 2025 Form 10-K.
Consolidation	The financial statements include the accounts of GLRE and the consolidated financial statements of its wholly-owned subsidiaries and all significant intercompany transactions and balances have been eliminated on consolidation.
Reclassifications	Reclassifications During the three and nine months ended September 30, 2026, the Company has reclassified certain expenses incurred by Syndicate 3456 from acquisition costs to underwriting expenses. Accordingly, the prior period condensed consolidated statements of operations have been reclassified to conform to the presentation of the current condensed consolidated statements of operations, in addition to the Innovations segment in Note 17.
Recently Issued Accounting Standards Not Yet Adopted	Recently Issued Accounting Standards Not Yet Adopted In November 2024, the FASB issued ASU 2024-03, Disaggregation of Income Statement Expenses (“ASU 2024-03”). This ASU 2024-03 requires more detailed disclosures about the type of expenses (including employee compensation, and depreciation / amortization) in commonly presented expense captions in the condensed consolidated income statements. ASU 2024-03 is effective for public business entities for fiscal years beginning after December 15, 2026, and interim periods within fiscal years after December 15, 2027. Early adoption is permitted. As this ASU relates solely to financial statement disclosure, its adoption will not impact the Company's results of operations, financial condition, or liquidity.

SIGNIFICANT ACCOUNTING POLICIES (Policies)

9 Months Ended

Sep. 30, 2026

These unaudited condensed consolidated financial statements (the “financial statements”) have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) for interim financial information, and with the U.S. Securities and Exchange Commission’s (“SEC”) instructions to Quarterly Report on Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all the information and footnotes required by U.S. GAAP for complete financial statements. The financial statements should be read in conjunction with the Company’s audited consolidated financial statements included in the Company’s 2025 Form 10-K.

Consolidation

The financial statements include the accounts of GLRE and the consolidated financial statements of its wholly-owned subsidiaries and all significant intercompany transactions and balances have been eliminated on consolidation.

Reclassifications

During the three and nine months ended September 30, 2026, the Company has reclassified certain expenses incurred by Syndicate 3456 from acquisition costs to underwriting expenses. Accordingly, the prior period condensed consolidated statements of operations have been reclassified to conform to the presentation of the current condensed consolidated statements of operations, in addition to the Innovations segment in Note 17.

Recently Issued Accounting Standards Not Yet Adopted

In November 2024, the FASB issued ASU 2024-03, Disaggregation of Income Statement Expenses (“ASU 2024-03”). This ASU 2024-03 requires more detailed disclosures about the type of expenses (including employee compensation, and depreciation / amortization) in commonly presented expense captions in the condensed consolidated income statements. ASU 2024-03 is effective for public business entities for fiscal years beginning after December 15, 2026, and interim periods within fiscal years after December 15, 2027. Early adoption is permitted. As this ASU relates solely to financial statement disclosure, its adoption will not impact the Company's results of operations, financial condition, or liquidity.