Bermuda-based Willis Group Holdings Ltd., the world's third largest insurance broker, plans to buy San Francisco-based brokerage firm Goldman Insurance Services for an undisclosed amount in a stock-and-cash deal.

Privately held Goldman, which places property/casualty and employee benefits coverage, mainly for middle market policy holders, handles total annual premiums of approximately $160 million and revenues in excess of $10 million.

Goldman's operations will be combined with those of Willis' existing San Francisco office. The deal is expected to close December 31.