Famous for his New York swagger, unconventional management style and “anything is possible” mantra, Willis CEO Joe Plumeri is to step down after 12 years running the world’s third-largest brokerage.

His replacement, McKinsey & Company Senior Partner Dominic Casserley, has surprised some analysts, who expected an industry insider rather than another executive with little insurance broking experience.

Mr Casserley’s recruitment has parallels with the appointment of Aon CEO Greg Case, who was headhunted from the same management advisory firm in 2005.

Mr Casserley will replace Mr Plumeri at the New York office on January 7, with the latter to serve as a non-executive chairman until next July.

Mr Plumeri says he is “proud beyond words” of Willis’ achievements since he took over the once-floundering broker in 2000 – two years after it was bought by leveraged buyout firm KKR for $US1.4 billion ($1.34 billion).

“In the past and in the future, it is our people who provide expertise, uphold our values and put a human face on the Willis cause for every one of our clients,” he said.

Mr Plumeri was Willis’ first non-British chief – and the industry’s first non-insurance CEO – and he immediately stamped his mark on the UK institution.

He shut down internal email for a day so staff would speak to each other and ordered that all office doors remain open – and in some cases be removed. It was a dramatic break from his predecessor, who operated his own floor and private lift in Willis’ London office.

Mr Plumeri was fiercely opposed to contingency commissions and banned the practice at the company in 2004. Willis, alongside Marsh & McLennan and Aon, paid more than $US2 billion ($1.9 billion) in combined fines following an investigation into the practice in 2005 and 2006.

A ban on contingency commissions in the US was lifted in 2010 but Willis continued to work without them until April this year, when Mr Plumeri reintroduced them on employee benefits lines only.

In 2008 he headed Willis’ $US2.1 billion ($2.02 billion) acquisition of rival Hilb, Rogal and Hobbs.