Warren Buffett has a reputation as one of the greatest investors of all time — and the track record to back it up.

Since taking over as the CEO of Berkshire Hathaway (NYSE: BRK.A) (NYSE: BRK.B) in 1965, he’s produced a compound average annual return of 19.8% for its investors. He’s done that by following his late partner Charlie Munger‘s advice to buy wonderful businesses at fair prices. Those show up as wholly owned subsidiaries within the growing Berkshire conglomerate, as well as equity investments in its portfolio.

Like all large institutional investors, Berkshire Hathaway is required by the Securities and Exchange Commission to publish its equity portfolio’s holdings for the public using form 13F every quarter. Following Buffett’s portfolio can provide a lot of great investment ideas and insight into how he thinks about portfolio management.

The Oracle of Omaha made several significant moves in the portfolio in the third quarter. He sold shares of Apple and revealed a stake in Chubb. He and his fellow portfolio managers also continued to add to Berkshire’s significant stakes in Occidental Petroleum and Liberty Media.

But two of his biggest purchases for Berkshire won’t show up in the portfolio at all. You’ll have to dig into Berkshire’s most recent quarterly earnings report to see where Buffett is investing Berkshire’s money.

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Buffett bought more of his favorite stock

There’s one stock Buffett has bought in each of the last 23 quarters dating back to mid-2018, and last quarter was no exception. He spent $2.6 billion buying back shares of Berkshire Hathaway. That’s more than he spent on any single stock in the first quarter. (Note: Combined purchases of Class A and Class C shares of Liberty Media exceeded $2.6 billion.)

The board of directors updated Berkshire’s share repurchase program in 2018 to allow Buffett to buy back shares as long as he considered the price per share to be below the intrinsic value of the stock, as determined on a conservative basis. As long as he kept at least $30 billion of cash on Berkshire’s balance sheet, he could buy as much of the stock as he felt was appropriate.

Buffett’s spent more buying back shares of Berkshire over the past six years than he’s spent on any other equity investment. Every time Buffett repurchases shares, he gives remaining shareholders a larger stake in everything Berkshire owns, including its core insurance operations, its railroad business, its equity portfolio, and its portfolio of other cash-flowing businesses.

Buffett’s decision to buy Berkshire stock has paid off handsomely for shareholders over the past five years. Shares currently trade near an all-time high, which means Buffett got a relative bargain on his previous purchases. Even today, the stock is a good value, with shares trading around 19 times forward earnings estimates. When you remove the balance of its cash and equity portfolio, core operations are valued at just $322 billion, which is less than 9 times last year’s core operating earnings.

It’s a good bet Buffett will continue to buy back stock going forward, and remaining shareholders will keep growing their portion of Berkshire’s profits as a result.

Buffett added over $21 billion to his largest holding

Many think of Apple as Buffett’s largest investment holding for Berkshire Hathaway, but another asset has taken over in the past year or so. Berkshire Hathaway holds about $189 billion in cash and Treasury bills on its balance sheet. By comparison, its Apple stake is worth about $150 billion.

Buffett continued to add to his Treasury bills last quarter. He even sold some of Berkshire’s stake in Apple, mostly using the proceeds to buy more Treasuries. The balance increased by more than $21 billion when you factor in stock sales and Berkshire’s cash flow from its core operations.

Treasury bills are Buffett’s default place to keep cash while looking for a good business or stock to buy. Treasury bills refer to U.S. government bonds maturing within one year, but most of Buffett’s holdings mature within six months. That typically means accepting a lower interest rate in exchange for the greater flexibility of shorter-dated bonds. Right now, however, Buffett’s benefiting from expectations for lower interest rates in the future, giving him a higher yield on his short-term loan to the government than he would get buying debt with longer maturities.

But Buffett isn’t just sitting on the sidelines due to high interest rates. He simply doesn’t see any great investment opportunities in the market for Berkshire Hathaway. He bought a sizable stake in Chubb over the last three quarters, but that’s only amounted to a position worth about $6.9 billion despite buying up over 6% of shares outstanding. Buffett’s biggest challenge has become finding an investment sizable enough that it can truly move the needle for Berkshire, which has become the seventh-largest publicly traded company.

While Buffett’s Treasury bills won’t show up in Berkshire’s portfolio, they’re becoming impossible to ignore for investors. It’ll take a significant change in market conditions for Buffett to put the growing cash pile to work.

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