OLDWICK, N.J.--(BUSINESS WIRE)--A.M. Best has assigned an issuer credit rating (ICR) of bbb- to James River Group Holdings, Ltd. (Holdings) [NASDAQ:JRVR]. The outlook assigned to the rating is positive. Concurrently, A.M. Best has affirmed the financial strength rating (FSR) of A- (Excellent) and the ICR of “a-” of JRG Reinsurance Company, Ltd. (JRG Re) and its U.S.-based insurance affiliates. The outlook for both ratings is positive. Holdings and JRG Re are both domiciled in Hamilton, Bermuda,