ST. LOUIS (AP) — The longtime chief executive officer for Ameren Corp. will become executive chairman, and another veteran of the utility will become CEO.

St. Louis-based Ameren announced Monday that Marty Lyons will replace Warner Baxter as president and CEO starting Jan. 1. Lyons joined Ameren in 2001 as vice president and controller. He served as chief financial officer for a decade and is currently president of Ameren Missouri.

Under the new arrangement, Baxter will remain an employee of Ameren, and Lyons will report to him. Baxter has been with Ameren since 1995 and has been president and CEO since 2014.