(Bloomberg) -- Berkshire Hathaway Inc. won the top financial-strength rating from A.M. Best Co. for a unit that plans to sell insurance directly to businesses over the Internet, paving the way for Chairman Warren Buffett to expand his company’s insurance operations. Berkshire Hathaway Direct Insurance Co. will initially focus on workers’ compensation and business owners’ package policies, A.M. Best said Thursday in a statement announcing that it had assigned the A++ grade to the company. Insurers typically require such ratings to begin operations.