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Quarterly filed Form 13Fs provide a way for investors to track the buying and selling activity of Wall Street's top money managers. Warren Buffett is occasionally granted the "confidential treatment" tag,

Warren Buffett's Berkshire Hathaway built a $1.6 billion stake in UnitedHealth last quarter, marking one of its last wagers with the investor as CEO.

Berkshire Hathaway's $1.6 billion stake in UnitedHealth Group is helping to lift the Dow Jones Industrial Average to a new record as investors pile into healthcare sector funds.

Berkshire Hathaway ( BRK.A -0.05%) ( BRK.B 0.24%) is considered by many to be a reliable stock for long-term investors. It's outperformed the S&P 500 ever since a young Warren Buffett took over the company in 1965, and its evolution from an aging textile maker to a diversified conglomerate churned out millionaire-making gains.

Warren Buffett is known for seeking out stocks of companies that possess wide economic moats — businesses with durable competitive advantages that fend off rivals and ensure long-term profitability. These moats,

UNH stock soared after Warren Buffett’s Berkshire Hathaway revealed it bought shares of the healthcare company. Nonetheless, UnitedHealth faces a long list of unresolved issues.

Leveraged positions in the stock market jumped 18% in one month and topped $1 trillion for the first time. Increasing use of debt to invest can tell us a lot about investors' attitudes. And while this has always been the case,