Warren Buffett's company is expected to file a quarterly update on its U.S. stock portfolio with regulators Thursday afternoon.

The documents Omaha-based Berkshire Hathaway is expected to file with the Securities and Exchange Commission will show the stocks it owned at the end of March.

Many investors watch these quarterly filings closely because they like to copy moves Buffett makes because of his remarkably successful record.

But two other Berkshire Hathaway executives each manage about $7 billion for the company, so it can be hard to determine who is making the moves.

Buffett has said investments smaller than $300 million are likely to be the work of other Berkshire managers.

Besides investments, Berkshire owns more than 80 subsidiaries in a variety of industries, including insurance, utilities, railroads, retail and manufacturing.