Michael Bloomberg will resume his role at Bloomberg LLC, where he owns an 88 percent stake, at the end of the year as his deputy, Dan Doctoroff, steps out of the picture.

Bloomberg, Doctoroff
Bloomberg, Doctoroff

The 72-year-old billionaire was NYC's Mayor eight months ago after serving three terms.

Bloomberg said he never intended to return to the helm of the media and financial data company, but after spending more time there during his retirement from public service discovered he really missed the place.

Since exiting City Hall, Bloomberg has been busy tackling issues such as public health, gun control and immigration reform.

Doctoroff, 56, served six years as NYC's Deputy Mayor for Economic Development and Rebuilding before joining Bloomberg as president in 2008. He became CEO in 2011.

Bloomberg called him one his closest colleagues and friends for the past 13 years.

He thanked Bloomberg "for giving me the honor of being the steward of his great company."

Bloomberg LLC, according to Doctoroff, "has always been Mike’s company and given his renewed interest and energy, it only makes sense for him to retake the helm."

Prior to Bloomberg, Doctoroff was managing partner at Oak Hill Capital and investment banker at Lehman Brothers.

He led NYC's unsuccessful effort to win the 2012 Olympic Games.