Former New York Mayor Michael Bloomberg is returning to lead Bloomberg LP, the media empire he founded and which he remains its majority shareholder.

The company said that Daniel Doctoroff will step aside as president and CEO of the company at the end of this year.

“Bloomberg LP will not name a replacement, but rather will again be led by Mr. Bloomberg with support from the existing leadership team,” the company said.

Doctoroff joined Bloomberg LP as president in January, 2008, and became its CEO in July, 2011. He had served in Bloomberg’s administration in New York, serving as deputy mayor for economic development and rebuilding.

Doctoroff reportedly decided to step down after Bloomberg began taking a greater role at the company since he left office as New York mayor earlier this year.

Bloomberg had said that he was not planning to return to run Bloomberg LP, and instead concentrate on his philanthropy, but but that he accepted the offer to return “after significant pushback and great reluctance.”

“This is a sad day for me and my company,” Bloomberg said in a statement.  “I really wanted Dan to stay and continue in his leadership role. But I understand his decision.  I never intended to come back to Bloomberg LP after twelve years as Mayor.  However, the more time I spent reacquainting myself with the company, the more exciting and interesting I found it – in large part, due to Dan’s efforts.  I have gotten very involved in the company again and that led to Dan coming to me recently to say he thought it would be best for him to turn the leadership of the company back to me.  It was a gracious and thoughtful offer and one that I finally accepted after significant pushback and great reluctance.”

Doctoroff said in a statement, “I love the company and have deep respect and affection for Mike, so leaving is not an easy decision, but it is the right one for the company, for Mike and for me at this stage of my life.  It is and has always been Mike’s company and given his renewed interest and energy, it only makes sense for him to retake the helm.”

During Doctoroff’s tenure, company revenues increased to $9 billion in 2014, from $5.4 billion in 2007.