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.

Buffett owned UnitedHealth shares before selling his stake in 2010, though his Berkshire Hathaway recently acquired shares.

Warren Buffett secret stock purchase has been kept confidential for months to avoid triggering copycat trades.

The biggest immediate changes will be that different people will be in control of the company's stock portfolio, and Abel will have power over Berkshire's $344 billion cash hoard. However, portfolio managers Ted Weschler and Todd Combs have been managing more of Berkshire's investments as the years have progressed.

UnitedHealth shares surged Friday after Warren Buffett’s Berkshire Hathaway revealed a stake in the embattled healthcare giant. Monitor these major chart levels.

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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,

Warren Buffett’s Berkshire Hathaway revealed a position in embattled healthcare giant UnitedHealth Group while showing smaller stakes in longtime holdings Apple and Bank of America, according to a regulatory filing Thursday.