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W.R. Berkley is an insurance holding company with a host of subsidiaries that primarily underwrite commercial casualty insurance. The firm specializes in niche products that include various excess and surplus lines, workers' compensation insurance, self-insurance consulting, reinsurance, and regional commercial lines for small and midsize businesses.

Berkshire Hathaway is a holding company with a wide array of subsidiaries engaged in diverse activities. The firm's core business segment is insurance, run primarily through Geico, Berkshire Hathaway Reinsurance Group, and Berkshire Hathaway Primary Group. Berkshire has used the excess cash thrown off from its operations to acquire Burlington Northern Santa Fe (railroad), Berkshire Hathaway Energy (utilities and energy distributors), and the companies that make up its manufacturing, service, and retailing operations (which include Precision Castparts, Lubrizol, Clayton Homes, Marmon, and IMC/ISCAR). The conglomerate is unique in that it is run on a completely decentralized basis.