Nasdaq said on Monday that its long-time chief executive Robert Greifeld would retire and that Adena Friedman, president and chief operating officer, would become CEO as of Jan. 1.

Greifeld, 59, has headed the trans-Atlantic stock exchange operator since 2003 and wrote his graduate thesis on the operation of the exchange. He will become chairman of Nasdaq‘s board, the company said. Current chairman Borje Ekholm will remain a board member.

Friedman, 47, has said she grew up at Nasdaq, where she started as an intern right out of business school and worked for 18 years before leaving the company in 2011 to join private equity firm Carlyle Group LP as chief financial officer. Friedman returned to Nasdaq in 2014 as president with an understanding she would succeed Greifeld, sources told Reuters at the time.

 

Friedman will retain the title of president, while no new COO has been named, the company said.

“Bob has done a tremendous job over the past 14 years of transforming the business and I’ve been with him for most of that journey,” Friedman said in an interview.

“My job will be to continue to ensure that we have growth opportunities and that we execute well on them.”

Under Greifeld, Nasdaq grew through a string of acquisitions, including OMX Group, INET, the Philadelphia and Boston Exchanges.

Many of the deals diversified Nasdaq away from transaction businesses and toward businesses that have more stable sources of income, such as providing technology, data, and corporate services to companies. In March, however, Nasdaq agreed to acquire U.S. options exchange operator International Securities Exchange for $1.1 billion.