Buffett, through Berkshire, bought more than 5 million shares of the managed care company, worth an estimated $1.6 billion. Meanwhile, Michael Burry, who became famous in the book and movie The Big Short for his bet against subprime mortgages, bought 20,000 shares. Billionaire David Tepper also increased his stake in the name during the quarter.

Warren Buffett's Berkshire Hathaway increased its holdings in UnitedHealth Group stock, and also added positions in D.R. Horton, Lamar Advertising, and Nucor.

Internet investing sites and tips give people a false — and costly — sense of their abilities, studies show. Legendary investor Howard Marks has a solution.