Warren Buffett's Berkshire Hathaway has acquired 5 million shares in UnitedHealth Group , a regulatory filing showed on Thursday, sending the health insurer's stock up 7% in extended trading.

Berkshire Hathaway revealed four new investments Thursday in steelmaker Nucor, insurer UnitedHealth and two of the nation’s biggest homebuilders — Lennar and DR Horton — but only one of the investments was big enough to ensure that legendary investor Warren Buffett may have handled them.

What Happened: The undisclosed investments of Berkshire Hathaway have been made public. The company has reportedly invested in steelmaker Nucor NUE +1.07% Get Free Report , homebuilders D.R. Horton DHI +1.30% Get Free Report and Lennar LEN +1.56% Get Free Report , with the total investments amounting to $1.8 billion.

TheStreet. On May 2, the day before Warren Buffett said he would retire at the end of 2025, Berkshire Hathaway shares hit a record. And then the stocks tumbled, about 14.5% for each class, just about every day until early August.

Berkshire Hathaway’s portfolio added six new stocks, including the three new secret stocks. Warren Buffett was a net seller of stocks for the eleventh straight quarter.

The Oracle’s of Omaha’s Surprising Reveal Investors worldwide hang on every utterance from Warren Buffett,. His annual shareholder letters are dissected for wisdom, and his quarterly SEC 13F filings trigger market speculation.

UnitedHealth Got a Boost From Berkshire’s Buying. 2 Reasons to Wait to Follow. UnitedHealth Group, the worst-performing stock in the Dow Jones Industrial Average so far this year, got a major boost last week from billionaire investor Warren Buffett. That doesn’t mean everyone else should buy.

Berkshire Hathaway’s $1 billion homebuilding investment indicates Warren Buffett’s confidence in a future U.S. housing market rebound.

Like Amazon CEO Andy Jassy, keeping a positive attitude helps the Warren Buffett-backed leader stay motivated toward success.

Warren Buffett emphasizes that while achieving success is exciting, effectively correcting mistakes when they occur is equally critical for businesses.