NEW YORK (AP) — PartnerRe's biggest shareholder, Italian investment company Exor, is buying the reinsurer in a deal worth about $6.9 billion. PartnerRe is ending its all-stock agreement with Axis Capital Holdings Ltd., which was made in January, in order to move ahead with a combination with Exor. PartnerRe previously rejected a $6.16 billion bid from Exor. Exor S.p.A.