The mystery stock could be the highlight of the new 13-F report. Berkshire was a light buyer of stocks in the second quarter, purchasing nearly $4 billion, while selling about $7 billion, indicating it continued to pare its equity portfolio, based on information in the 10-Q for the period.

Some of the world’s wealthiest people joined Warren Buffett’s Berkshire Hathaway Inc. in buying shares of embattled insurer UnitedHealth Group Inc. in the second quarter.

“We think that most of their problems, if not all of them, are temporary in nature,” says Marshfield’s co-portfolio manager Elise Hoffmann.

Warren Buffett's Berkshire Hathaway disclosed on Thursday a new investment in UnitedHealth Group after the insurer became a target for many Americans upset over the direction of the nation's healthcare.

The blue-chip Dow Jones ended higher after hitting an intraday record high on Friday, as UnitedHealth's shares jumped after Berkshire Hathaway raised its stake, but other Wall Street indexes slipped ...

However, recent labor market weakness and signs that tariff-induced inflation was yet to reflect in headline consumer prices have made investors confident of a potential dovish move next month.