Thomas B. Leonardi is stepping down as commissioner of the Connecticut Insurance Department to become senior adviser for a leading investment banking firm.

The announcement came Wednesday from Gov. Dannel P. Malloy, who named Leonardi to head the insurance department at the beginning of his first term. No successor was immediately named.

Among Leonardi’s accomplishments were the creation of Connecticut’s first dedicated captive insurance division, leading to the state being named No. 2 in the nation in terms of its regulatory atmosphere on self-insurance. Under Leonardi, the state also recovered nearly $4 million a year by following up on consumer complaints and helped out homeowners devastated by the effects of Superstorm Sandy, Hurricane Irene and other weather-related incidents.

“Thanks to the diligence of Thomas Leonardi’s work in my administration, Connecticut has reclaimed its reputation as the insurance capital of the world, and our international influence has never been higher,” Malloy said in a statement. “I have no doubt that Tom’s global reputation as a recognized expert on a variety of regulatory issues, along with the outstanding relationships he has built with consumer and industry trade associations, played a crucial role.”

Leonardi plans to step down in December and take a new position with the New York-based Evercore, giving advice on insurance matters. He previously had served as chief executive of Avon-based Northington Partners Inc., specializing in insurance matters.

Other accomplishments cited during Leonardi’s tenure were his work with the Connecticut Health Insurance Exchange as it geared up to implement the Affordable Care Act; social media outreach using Twitter, Facebook and You Tube, as well as an award-winning television campaign, and the integration of insurance issues into the Governor’s Emergency Operations Center during weather disasters.

l.howard@theday.com

Twitter: @KingstonLeeHow