That conclusion is further supported by the fact that Berkshire had $277 billion in cash and U.S. Treasuries on its balance sheet as of the June quarter, another record for the company. Finally, Buffett repurchased a mere $345 million in Berkshire stock during the June quarter, which marks his smallest allocation to stock buybacks in six years.

Warren Buffett's turn to cash indicates that now is not the best time for high equity exposure, David Einhorn wrote.

U.S. stocks are rising Wednesday following better-than-expected profit reports from Morgan Stanley, United Airlines and other big companies. The S&P 500 was 0.5% higher in afternoon trading, a day after sliding from its all-time high because of tumbling energy and technology stocks.

In fact, Berkshire actually holds two S&P 500 index funds in its portfolio: the Vanguard S&P 500 ETF ( VOO 0.42%) and the SPDR S&P 500 ETF Trust ( SPY 0.43%). One top analyst on Wall Street predicts the S&P 500 will hit 15,000 by 2030, and if he's right, those index funds could deliver a return of 158% from here!

Goldman Sachs, UBS, BMO, and Deutsche Bank have raised their S&P 500 price targets in recent weeks as the index continues to hit record highs.