Hartford Financial Services Group Inc. has reached a deal to buy insurance underwriter Navigators Group Inc. for $2.1 billion, as the company seeks to expand its specialty lines of business for growth, the Wall Street Journal reported. The purchase of Navigators, which will bring its global marine, construction and energy liability lines of business to Hartford, comes less than a year after Hartford agreed to acquire a unit of Aetna Inc. that provides insurance products to U.S. employers’ benefits programs.