W. R. Berkley Corporation is an insurance holding company that is among the largest commercial lines writers in the United States and operates in three segments of the property casualty insurance business: insurance-domestic, insurance-international and reinsurance-global.

W. R. Berkley Corporation is an insurance holding company that is among the largest commercial lines writers in the United States and operates in three segments of the property casualty insurance business: insurance-domestic, insurance-international and reinsurance-global.