Blue Cross-Blue Shield insurer Anthem has picked a former top executive from its biggest competitor to replace Joseph Swedish as its next CEO.

Anthem says Gail K. Boudreaux will start Nov. 20. Swedish will serve as executive chairman until May and then as senior advisor for a couple more years.

A statement Monday from Indianapolis-based Anthem gave no reason for the departure of Swedish, who has led the insurer for more than four years.

Boudreaux, 57, served as a CEO of UnitedHealthcare, the health insurance arm of UnitedHealth Group Inc., until November 2014.

Minnetonka, Minnesota-based UnitedHealth and Anthem Inc. are the nation's two largest health insurers based on enrollment. Those companies and other major insurers have seen their stock prices jump at least 50 percent in the last 12 months.