As part of the transaction, Hewitt shareholders will receive a combination of cash and Aon Corp. stock totaling $4.9 billion based on the July 9 closing price of Aon's shares.
Earlier in the day, stockholders of Hewitt approved adoption of the Agreement and Plan of Merger at a special meeting of Hewitt's stockholders. Completion of the transaction remains subject to customary closing conditions, including the receipt of certain regulatory approvals.
Chicago-based Aon said it hopes to complete the transaction by mid-November. At that point, it plans to integrate Hewitt and its Aon Consulting unit and change the name of the consulting operations to Aon Hewitt.
Aon Hewitt would generate about $4.3 billion in annual revenues and have about 29,000 employees.