Related Party Transactions	12 Months Ended
Related Party Transactions	Dec. 31, 2020
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions William M. Rue, a Director of the Parent, is Chairman of, and owns more than 10% of the equity of Rue Holding Company, which owns 100% of Chas. E. Rue & Son, Inc., t/a Rue Insurance, a general independent retail insurance agency ("Rue Insurance"). Rue Insurance is an appointed distribution partner of the Insurance Subsidiaries on terms and conditions similar to those of our other distribution partners, which includes the right to participate in the Agent Plan. Mr. Rue’s son is President, and an employee, of Rue Insurance, and owns more than 10% of the equity of Rue Holding Company. Mr. Rue’s daughter is an employee of Rue Insurance and owns less than 10% of the equity of Rue Holding Company. Our relationship with Rue Insurance has existed since 1928. Rue Insurance placed insurance policies with the Insurance Subsidiaries for its customers and itself. Direct premiums written associated with these policies were $11.0 million in both 2020 and 2019, and $10.1 million in 2018. In return, the Insurance Subsidiaries paid standard market commissions, including supplemental commissions, to Rue Insurance of $1.8 million in 2020, $2.0 million in 2019, and $2.1 million in 2018. Amounts due to Rue Insurance at December 31, 2020 and December 31, 2019 were $0.2 million and $0.3 million, respectively. All contracts and transactions with Rue Insurance were consummated in the ordinary course of business on an arm's-length basis. In 2005, we established a private foundation, now named The Selective Insurance Group Foundation (the "Foundation"), under Section 501(c)(3) of the Internal Revenue Code. The Board of the Foundation is comprised of some of the Parent's officers. We made $0.5 million of contributions to the Foundation in 2020 and 2018, and $1.3 million in 2019. BlackRock, Inc., a leading publicly-traded investment management firm (“BlackRock”), has purchased our common shares in the ordinary course of its investment business and has previously filed Schedules 13G/A with the SEC. On January 27, 2021, BlackRock filed a Schedule 13G/A reporting beneficial ownership as of December 31, 2020, of 11.2% of our common stock. In connection with purchasing our common shares, BlackRock filed the necessary filings with insurance regulatory authorities. On the basis of those filings, BlackRock is deemed not to be a controlling person for the purposes of applicable insurance law. We are required to disclose related party information for our transactions with BlackRock. BlackRock is highly regulated, serves its clients as a fiduciary, and has a diverse platform of active (alpha) and index (beta) investment strategies across asset classes that enables it to tailor investment outcomes and asset allocation solutions for clients. BlackRock also offers the BlackRock Solutions® investment and risk management technology platform, Aladdin®, risk analytics, advisory, and technology services and solutions to a broad base of institutional and wealth management investors. We incurred expenses related to BlackRock for services rendered of $2.0 million in 2020, $2.2 million in 2019, and $2.0 million in 2018. Amounts payable for such services at December 31, 2020 and December 31, 2019, were $1.3 million and $1.1 million, respectively. As part of our overall investment diversification, we invest in various BlackRock funds from time to time. These funds accounted for less than 1% of our invested assets at December 31, 2020 and December 31, 2019, and are predominately reflected in Equity securities on our Consolidated Balance Sheet. During 2020, with regard to BlackRock funds, we (i) purchased $62.2 million, (ii) recognized net unrealized losses of $0.2 million, and (iii) recorded in $0.4 million income. We did not make any sales for BlackRock funds in 2020. During 2019, we purchased $21.7 million in securities, (ii) sold $59.5 million, (iii) recognized net realized and unrealized gains of $5.7 million, and (iv) recorded $0.8 million in income. During 2018, we purchased $41.4 million in securities and recognized a net realized and unrealized loss of $3.6 million. There were no amounts payable on the settlement of these investment transactions at December 31, 2020 and December 31, 2019. Our Pension Plan's investment portfolio contained investments in BlackRock funds of $191.8 million at December 31, 2020 and $144.2 million at December 31, 2019. During 2020, with regard to BlackRock funds, the Pension Plan (i) purchased $56.7 million, (ii) sold $44.9 million, and (iii) recorded net investment income of $35.8 million. In 2019, with regard to BlackRock funds, the Pension Plan (i) purchased $19.7 million, (ii) sold $44.1 million, and (iii) recorded net investment income of $36.7 million. In 2018, with regard to BlackRock funds, the Pension Plan (i) purchased $132.5 million, (ii) sold $125.6 million, and (iii) recorded net investment income of $9.3 million. In addition, our Deferred Compensation Plan and Retirement Savings Plan may offer our employees the option to invest in various BlackRock funds. All contracts and transactions with BlackRock were consummated in the ordinary course of business on an arm's-length basis.