In a surprising move, Todd Nelson has reportedly resigned his position as CEO of the Apollo Group. The Apollo Group is the parent organization of the for-profit University of Phoenix, the world's largest private college network.

Nelson, CEO and president since 1998, had worked for the company for almost 20 years. Since 1995, Apollo's stock has risen almost 8,000 percent. With that rise, Nelson and many other Apollo executives had become multi-millionaires.

According to the Arizona Republic, Nelson's salary and bonuses exceeded $5 million for 2004. At the time of his departure, the former CEO also owned unexercised stock options of more than $17.8 million.

Though the Nelson oversaw the rise of the University to 250,000 students and its accompanying stock growth, shares in the company had fallen 25 percent over the past year. Those losses came in large part due to fines Phoenix had to pay for violations of unpaid overtime as well as other regulatory problems.

Prior to 2005, Apollo's stock had consistently been one of the biggest Wall Street success stories since the company went public back in 1994.