W. R. Berkley Corporation is an insurance holding company. It operates through two segments: Insurance and Reinsurance-Global. The Insurance segment consists of its commercial insurance business operations, comprising excess and surplus lines, and admitted lines, throughout the United States, as well as its insurance business operations in the United Kingdom, Continental Europe, South America, Canada, Mexico, Scandinavia, Asia and Australia. Its Insurance segment comprises business units, such as Acadia Insurance, American Mining Insurance Group, Berkley Accident and Health, Berkley Agribusiness Risk Specialists, Berkley Aviation and Berkley Canada. Reinsurance consists of its reinsurance business on a facultative and treaty basis, in the United States, the United Kingdom, Continental Europe, Australia, the Asia-Pacific region and South Africa. Its Reinsurance segment comprises business units, such as Berkley Re America, Berkley Re Asia Pacific, Berkley Re Direct and Berkley Re UK.