OLDWICK, N.J.--( BUSINESS WIRE )-- A.M. Best Co. has affirmed the financial strength ratings (FSR) of A- (Excellent) and issuer credit ratings (ICR) of "a-" for the majority of the insurance subsidiaries of Humana Inc. (Humana) (Louisville, KY) ( NYS: HUM ). A.M. Best also has affirmed Humana's ICR of "bbb-" and existing debt ratings. Ratings also have been assigned on new debt for Humana. The outlook for all ratings remains stable.