After four years at the helm of health insurance giant Anthem, CEO and president Joseph Swedish will hand over the reins to Gail Boudreaux, the former CEO of UnitedHealthcare, on Nov. 20.

The company announced the move on the morning of Nov. 6. Swedish will relinquish his titles as president and CEO, staying on as executive chairman of the Anthem board until May 2018 and as senior advisor through May 2020.

“The board wants to thank Joe Swedish for his visionary leadership and steadfast commitment to expanding access to high quality, affordable health care during a dynamic time for our company and our industry,” George A. Schaefer Jr., lead independent director on the Anthem board, said in a statement. “We are fortunate that, as a result of Joe’s leadership, we have a foundation of strong performance that allows us the opportunity to transition to a new chief executive officer.”

Schaefer said during Swedish’s tenure, Anthem’s membership has grown by 11 percent to 40 million, the average share price has tripled and operating revenue increased 39 percent to more than $89 billion. There have been controversies as well, such as the abandoned $54 billion acquisition of Cigna, losses in the individual market totaling $374 million in 2016 and the company’s decision to stop paying for outpatient imaging examinations performed in hospitals.

The press release from Anthem gave no reason for Swedish’s departure, with his comments limited to praising his successor.

“Gail is widely recognized as a very successful executive in the health care industry,” Swedish said. “I am confident that her depth of experience will be of great benefit to our company, our associates and our members. It has been a privilege to lead Anthem and work with our more than 53,000 associates across the nation. As we move ahead, I look forward to working closely with Gail in this new capacity.”

Beyond her executive experience at UnitedHealthcare—the largest insurer in the U.S. ahead of Anthem—Boudreaux has worked with other Blue Cross and Blue Shield (BCBS) plans, which Anthem operates in 14 states. She was president at BCBS of Illinois and served as executive vice president at Health Care Services Corporation, which runs BCBS plans in Illinois, New Mexico, Oklahoma and Texas.

“For more than 75 years, Anthem has worked tirelessly to make a positive difference in the lives of Americans,” Boudreaux said in a statement. “I’m honored to lead the organization into the future and continue to improve the lives of those we serve. We are dedicated to connecting our customers to the right resources so that they can realize their health care goals while simplifying the health care experience for them.”