W. R. Berkley Corporation is an insurance holding company which, through its subsidiaries, operates in five segments of the property casualty insurance business: specialty lines of insurance (including excess and surplus lines and commercial transportation); alternative markets (including the management of alternative insurance market mechanisms); reinsurance; regional property casualty insurance; and international. The Company's specialty insurance, alternative markets and reinsurance operations are conducted nationwide. Regional insurance operations are conducted primarily in the Midwest, New England, Southern (excluding Florida) and Mid Atlantic regions of the United States. International operations are conducted in Argentina and the Philippines.