Investors kickoff the week awaiting more developments on President Trump’s trade deals and the decision on interest rates by the Federal Reserve out Wednesday. Optimism is improving after the S&P 500 notched the longest winning streak in 20 years last week.

"You're losing one of the most esteemed investors one could argue of all time," a source said of investors' reaction to Buffett's plan to step down.

Billionaire investor Warren Buffett, 94, announced Saturday he will leave his role as Berkshire Hathaway’s CEO by the end of the year, telling investors about his decision at the firm’s annual shareholder meeting, where he addressed President Donald Trump’s tariffs, discussed Berkshire Hathaway’s business strategies and the larger economy.