CBSNina Tassler, who helmed CBS Entertainment since 2004, will step down by yearend and serve as consultant through 2017.

Glenn Geller, 43, programming chief at CBS Entertainment and TV studios group, has moved into the president post and creative affairs chief.

Les Moonves, CEO of CBS Corp., who has known Tassler for 25 years, said, "Nina is a creative executive with the instincts of an artist."

CBS is "grateful and proud" of her success at company "and will be the biggest fans of all her future endeavors," added Moonves.

Tassler, 58, has enjoyed programming hits such as "Madam Secretary," "The Good Wife," "Criminal Minds," "Blue Bloods," "Elementary," "The Big Bang Theory," and "Late Show with Stephen Colbert."

Under her guidance, CBS ranked as the top network for 12 of the past 13 years.

Moonves considers Geller the "obvious successor" to Tassler. "Glenn brings outstanding skills to all parts of the creative and production process< and he has led large programming teams both at the network and studio that oversee our biggest franchises and hit programs," said Moonves.