Insurance industry analysts aren't expecting major changes at Marsh & McLennan Cos. Inc. after Daniel S. Glaser succeeds Brian Duperreault as president and CEO of the New York-based company on Jan. 1, 2013.

MMC announced last week that Mr. Duperreault would retire at the end of the year. Mr. Glaser, MMC's group president and chief operating officer, was named as his successor. In addition, Mr. Duperreault will retire from MMC's board of directors and Mr. Glaser will become a member of the board on Jan. 1.

“Mr. Duperreault turned 65 this year and decided to retire,” a spokesman for MMC said.

Mr. Duperreault joined in early 2008 to lead the brokerage's turnaround after it became the center of a bid-rigging scandal sparked in 2004 by a lawsuit filed by then-New York Attorney General Eliot Spitzer. Marsh settled the suit for $850 million, but its business still struggled in the years that followed.

Before joining Marsh, Mr. Duperreault transformed Ace Ltd. into a global insurer and reinsurer. Before joining Ace, he was a longtime executive at American International Group Inc.

“We are immensely grateful to Brian for the significant turnaround the company accomplished under his stewardship,” said Lord Lang of Monkton, chairman of the board of directors of MMC, in a statement announcing Mr. Duperreault's retirement.

“Being part of the turnaround of Marsh & McLennan Cos. has been one of the most gratifying aspects of my career,” Mr. Duperreault said in a statement.

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Mr. Glaser joined MMC in 2007 to head retail brokerage unit Marsh Inc. Like Mr. Duperreault, he was a longtime AIG executive, although he had previously worked for MMC.

The change at the top should not lead to major changes at the organization, industry analysts say.

“I don't think it's very surprising,” said Mark Dwelle, an insurance analyst at RBC Capital Markets, a unit of RBC Dominion Securities Inc., in Richmond, Va. He said Mr. Glaser has “been front and center as the heir apparent” for some time.

“Initially, I wouldn't expect vast changes,” Mr. Dwelle said. He said Mr. Glaser has “been pretty deeply embedded in the senior management core there for several years.”

“I would be shocked if there are any noticeable changes,” said Meyer Shields, director at Stifel Nicolaus & Co. in Baltimore. “I think there's been an intentional campaign to have Dan Glaser assume a more public and prominent role.”

Keith Walsh, director of insurance research at Citi Investment Research in New York, also said the change in management should not mean significant changes at MMC.

“They put Dan Glaser in this role of COO 17 months ago, and that was really telegraphing to the Street that that was our guy to succeed Brain Duperreault,” he said.

“They didn't have the COO position before they put Dan in that position,” he said. “And Brian was very open from Day 1 about what he wanted to accomplish at Marsh, and he succeeded beyond everyone's expectations.”

Like Mr. Walsh, Messrs. Dwelle and Shields credited Mr. Duperreault with a job well done.

“When Mr. Duperreault came in four years ago, he was brought in to turn things around, and now he can say mission accomplished,” Mr. Dwelle said.

“Marsh turned around from a dreadfully struggling company into a powerhouse.”