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.

Warren Buffett's Berkshire Hathaway revealed a new stake in troubled insurer UnitedHealth, according to a regulatory filing. The Omaha-based conglomerate bought more than 5 million shares in the health care firm for a stake worth about $1.