Chicago-based insurance broker Aon Corp. said that David P. Bolger, executive vice president, chief financial officer and chief administrative officer, will leave the firm after the appointment of his successor.

A spokesman said Mr. Bolger and Aon reached a mutual decision that it was time to make a change in the company.

Aon said Mr. Bolger will remain with Aon for a period of time following the appointment of his successor in order to ensure an orderly transition. The company is commencing a search for a new CFO.

Mr. Bolger, 49, joined Aon in 2003. Prior to joining Aon, he served in various senior positions at Bank One Corporation and its predecessor companies, including American National Bank and First Chicago Corporation.

This story was updated at 12:10 p.m today.