The foreign exchange market works through financial institutions, and it operates on several levels. Behind the scenes banks turn to a smaller number of financial firms known as dealers, who are actively involved in large quantities of foreign exchange trading. Most foreign exchange dealers are banks, so this behind-the-scenes market is sometimes called the interbank market, although a few insurance companies and other kinds of financial firms are involved. Trades between foreign exchange dealers can be very large, involving hundreds of millions of dollars.[citation needed] Because of the sovereignty issue when involving two currencies, Forex has little (if any) supervisory entity regulating its actions.