Nina Tassler, who has seen CBS become the most-watched among the four major broadcast networks, is stepping down after leading CBS Entertainment for over a decade. She will be replaced by Glenn Geller.

Tassler will continue as CBS Entertainment president through at least 2017. She first took the role in 2004 and has been at the network since 1997. During her tenure in the top role, CBS’ roster of big hits has only grown with Criminal Minds, Elementary, The Good Wife and How I Met Your Mother. The Big Bang Theory also became the most-watched sitcom on television under her watch.

“Nina and I have been colleagues and friends for 25 years,” CBS President and CEO Les Moonves said in a statement. “It is one of the proudest partnerships of my professional life. We’ve enjoyed amazing success together, both here and at Warner Bros., and it’s been a privilege to watch her talents and accomplishments grow. Nina is a creative executive with the instincts of an artist, so it came as no surprise that she would eventually want to express those talents beyond television. All of us here are grateful and proud of CBS’s success with Nina leading our entertainment programming, and we will be the biggest fans for all her future endeavors.”

Geller has been at the network since 2001 and was promoted to Executive Vice President of Current Programming for CBS in June 2013. Moonves said that when Tassler said she was leaving, he immediately thought of Geller as her successor. Before CBS, he worked at 20th Century Fox TV’s drama department.

Under his current role, Geller oversees creative affairs for the NCIS shows, ZooThe Good Wife and The CW’sJane The Virgin.

“I pass the baton to Glenn with great confidence and pride. He is an outstanding leader with great respect for the artistic process and a clear vision for programming success,” Tassler said.

image of Nina Tassler: Monty Brinton/CBS