(Peter Foley/Bloomberg/Getty Images)

Warren Buffett invested almost $24 billion through his company Berkshire Hathaway in the third quarter, the most in 15 years, according to a regulatory filing.

The billionaire’s firm made investments beyond the usual financial and consumer sectors, including a 62 percent increase in “commercial, industrial and other” companies, totaling $17.4 billion.

Buffett’s investment included a $5 billion investment in embattled giant, Bank of America, announced in August. Berkshire Hathaway, based in Omaha, Neb., also completed its $9 billion acquisition of chemical company, Lubrizol, in September.  The filing doesn’t state what Buffett is pouring his cash into though he has large stakes in firms like Coca-Cola and Wells Fargo. He’s made some investing blunders in the past as well.

Berkshire Hathaway released the investment information on Friday, as part of its third-quarter earnings announcement.  For the three months that ended Sept. 30, net income fell to $2.28 billion from $3 billion in the same quarter last year.

The successful businessman’s decisions are closely followed by investors around the globe. Buffett, worth about $39 billion, is the second-richest person in the U.S. after Gates ($59 billion), according to Forbes’ list of richest people in the country released in September.

Buffett reportedly increased his company’s investments in stocks as they suffered lows from the downgrade of U.S. debt last August and the European debt crisis. His widely-known investment philosophy is to hold stakes in quality companies for the long-haul, as opposed to participating in speculative trading.  While Berkshire Hathaway owns 80 companies like Dairy Queen, Geico Auto Insurance and See’s Candies, it has stakes in Coca-Cola and Wells Fargo, among other companies.

This year, Buffett has become more vocal in his pursuit to increase the tax rate for the wealthiest Americans, including revealing his tax returns to the public last month.