Basis of Presentation	9 Months Ended
Sep. 30, 2026
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The words “Company,” “we,” “us,” or “our” refer to Selective Insurance Group, Inc. (the “Parent”) and its subsidiaries, except as expressly indicated or the context requires otherwise. We have prepared our interim unaudited consolidated financial statements (“Financial Statements”) in conformity with (i) United States (“U.S.”) generally accepted accounting principles (“GAAP”), and (ii) the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”) regarding interim financial reporting. In preparing the Financial Statements, management is required to make estimates and assumptions that affect the reported assets and liabilities, the disclosure of contingent assets and liabilities, and the reported revenues and expenses. Actual results could differ from those estimates. All significant intercompany accounts and transactions are eliminated in consolidation. Our Financial Statements reflect all adjustments that we consider normal, recurring, and necessary for a fair presentation of our financial condition, results of operations and cash flow. Our Financial Statements cover the third quarters ended September 30, 2026 (“Third Quarter 2026”) and September 30, 2025 (“Third Quarter 2025”), and the nine-month periods ended September 30, 2026 (“Nine Months 2026”) and September 30, 2025 (“Nine Months 2025”). Our Financial Statements do not include all information and disclosures required by GAAP and the SEC for audited annual financial statements. Because interim period results of operations are not necessarily indicative of full-year results, our Financial Statements should be read in conjunction with the consolidated financial statements in our Annual Report on Form 10-K for the year ended December 31, 2025 (“2025 Annual Report”) filed with the SEC.

The words “Company,” “we,” “us,” or “our” refer to Selective Insurance Group, Inc. (the “Parent”) and its subsidiaries, except as expressly indicated or the context requires otherwise. We have prepared our interim unaudited consolidated financial statements (“Financial Statements”) in conformity with (i) United States (“U.S.”) generally accepted accounting principles (“GAAP”), and (ii) the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”) regarding interim financial reporting. In preparing the Financial Statements, management is required to make estimates and assumptions that affect the reported assets and liabilities, the disclosure of contingent assets and liabilities, and the reported revenues and expenses. Actual results could differ from those estimates. All significant intercompany accounts and transactions are eliminated in consolidation.

Our Financial Statements reflect all adjustments that we consider normal, recurring, and necessary for a fair presentation of our financial condition, results of operations and cash flow. Our Financial Statements cover the third quarters ended September 30, 2026 (“Third Quarter 2026”) and September 30, 2025 (“Third Quarter 2025”), and the nine-month periods ended September 30, 2026 (“Nine Months 2026”) and September 30, 2025 (“Nine Months 2025”). Our Financial Statements do not include all information and disclosures required by GAAP and the SEC for audited annual financial statements. Because interim period results of operations are not necessarily indicative of full-year results, our Financial Statements should be read in conjunction with the consolidated financial statements in our Annual Report on Form 10-K for the year ended December 31, 2025 (“2025 Annual Report”) filed with the SEC.