W. R. Berkley Corporation is an insurance holding company. It operates through two segments of the property casualty insurance business: Insurance and Reinsurance & Monoline Excess. Its Insurance businesses underwrite predominantly commercial insurance business, including excess and surplus lines, admitted lines and specialty personal lines throughout the United States, as well as insurance business in Asia, Australia, Canada, Continental Europe, Mexico, Scandinavia, South America and the United Kingdom. Its Insurance segment consists of business units, including Acadia Insurance, Admiral Insurance, Berkley Accident and Health, Berkley Agribusiness and others. Its Reinsurance & Monoline Excess segment offers reinsurance business on a facultative and treaty basis, primarily in the United States, United Kingdom, Continental Europe, Australia, the Asia-Pacific region and South Africa, as well as operations that solely retain risk on an excess basis and certain program management business.