One of the most secretive business enterprises in the Western world. The financial press is not allowed to publish any financial statistics on the firm whatever (unlike, say, Bechtel or Fidelity Investments, whose financials appear in Hoovers listings). Basically, it converts oil wealth into political influene through a huge web of "foundations."
Koch Industries operates enormous oil refineries in Alaska, Minnesota, and Texas; owns 4000 miles of pipeline; Brawny paper towels, Dixie cups, Georgia-Pacific lumber, Stainmaster carpet, and Lycra (fiber used to make Spandex).
Koch Family Foundations funnel immense amount of money to climate change denial groups, although they manage to remain secretive about that also. Both David and Charles Koch have assets easily in excess of $8 billion, and they are the largest political donors of the oil and gas industry. Mostly their "charitable foundations" promote far-right propaganda.
The Americans for Prosperity Foundation (formerly Citizens for a Sound Economy) and the Cato Institute are creations of the Koch Family Foundations.