AM Best has affirmed the Financial Strength Rating of A+ [Superior] and the Long-Term Issuer Credit Ratings of “aa-” [Superior] of the operating affiliates of Allied World Assurance Company Holdings, Ltd.’s [Allied World Holdings] [Bermuda], collectively referred to as Allied World. Concurrently, AM Best has affirmed the Long-Term ICRs of “a-” [Excellent] of Allied World …