Despite Buffett overseeing stakes in nearly four-dozen securities, the lion's share of Berkshire's invested assets have been put to work in seven top ideas.

It’s been a rocky week in the stock market. Warren Buffett’s Berkshire Hathaway has been buying. The Omaha, Neb., company boosted its positions in Occidental Petroleum, VeriSign and SiriusXM with stock purchases this Tuesday through Thursday,

Although Occidental Petroleum is already a major holding of Berkshire Hathaway, the company purchased an additional 8.9 million shares of Occidental last

Since Warren Buffett became the CEO of Berkshire Hathaway ( BRK.A 0.80%) ( BRK.B 0.95%) in 1965, its stock has delivered a compound annual return of 19.8%. That would have been enough to turn a $1,000 investment into $42.5 million, whereas the same investment in the S&P 500 would have grown to just $325,053 over the same period.

After spending much of Q3 selling shares of various companies including BAC, Warren Buffet is back to taking major long positions.