Berkshire Hathaway recently added 26 million shares of the insurer. Last month, investors finally learned the identity of the mystery stock Berkshire Hathaway had been accumulating for months: Chubb (CB -0.70%). Over three quarters, Berkshire added 26 million shares of the insurance company, stirring up interest from everyday investors. Chubb checks many boxes for investors looking to invest in a well-run company that consistently delivers. However, after getting a boost from Berkshire, the stock has increa ...