W. R. Berkley Corporation is an insurance holding company. The Company operates through two segments: Insurance and Reinsurance & Monoline Excess. The Insurance segment provides commercial insurance business, including excess and surplus lines, admitted lines and specialty personal lines throughout the United States, as well as insurance business in the United Kingdom, Continental Europe, South America, Canada, Mexico, Scandinavia, Asia and Australia. The Insurance segment provides business units, which include Acadia Insurance, Admiral Insurance, Berkley Agribusiness, Berkley Aspire, Berkley Asset and Berkley Canada. The Reinsurance & Monoline Excess segment provides reinsurance business on a facultative and treaty basis, primarily in the United States, the United Kingdom, Continental Europe, Australia, the Asia-Pacific region and South Africa. The Reinsurance segment consists of business units, including Berkley Re America, Berkley Re Asia Pacific and Berkley Re Solutions.