W. R. Berkley Corporation is an insurance holding company. The Company operates in the three segments of the property casualty insurance business: Insurance-Domestic, Insurance-International and Reinsurance-Global. Its Insurance-Domestic segment includes commercial insurance business, including excess and surplus lines and admitted lines, primarily throughout the United States. Its Insurance-Domestic operating units underwrite commercial insurance business primarily throughout the United States. The Company's Insurance-International segment includes insurance business primarily in the United Kingdom, Continental Europe, South America, Canada, Scandinavia, Asia and Australia. The Company's Reinsurance-Global segment includes 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.