Global investment firm Kohlberg Kravis Roberts & Co has agreed to acquire specialty insurance brokerage firm Alliant Insurance Services from Blackstone for an undisclosed sum.

Alliant’s management team and employees currently own nearly 45% of the company and following the deal will roll over a substantial portion of their investment in the firm.

JP Morgan Chase and Blackstone Advisory Partners served as advisers to Blackstone and Alliant on the transaction.

Subject to certain conditions, the acquisition is expected to close in the fourth quarter of 2012.

Established in 1925, Alliant Insurance is headquartered in Newport Beach and provides property and casualty, workers’ compensation, employee benefits, surety, and financial products and services to some 20,000 clients nationwide.

Founded in 1976, KKR has $66.3bn in assets under management as of September 30, 2012.

Blackstone is an investment and advisory firm offering various financial advisory services, including financial and strategic advisory, restructuring and reorganization advisory and fund placement services.