Aon Corp. (AON), the world's biggest insurance broker, revealed in a regulatory filing Thursday a restructuring plan which includes cutting 1,500 to 1,800 positions globally, as it combines the operations of the recently acquired Hewitt Associates with its own.

Aon completed the $4.9 billion acquisition of consulting firm Hewitt Associates, which was completed on October 1, 2010. The restructuring plan will continue through the end of 2013. As part of the plan, Aon estimates it will cut predominantly non-client facing positions.

The insurance conglomerate expects the restructuring to result in total annual savings of around $280 million in 2013. Additional savings from areas such as information technology, procurement and public company costs will result in a total savings of $355 million that year.

The restructuring plan will cost approximately $325 million, the company said, consisting of approximately $180 million in employee termination costs and approximately $145 million in real estate rationalization costs.

Hewitt has 29,000 employees globally, and Aon has more than 36,000 employees, according to the companies.