RLI Corp., an insurance holding company, underwrites property and casualty insurance in the United States and internationally. Its Casualty segment provides commercial and personal coverage products; and general liability products, such as coverage for third-party liability of commercial insureds, including manufacturers, contractors, apartments, and mercantile. It also offers coverages for security guards and in the areas of onshore energy-related businesses and environmental liability for underground storage tanks, contractors and asbestos, and environmental remediation specialists; and professional liability coverages focuses on providing errors and omission coverage to small to medium-sized design, technical, computer, and miscellaneous professionals.