KKR & Co., the private-equity firm run by Henry Kravis and George Roberts, agreed to buy brokerage Alliant Insurance Services Inc. from Blackstone Group LP for an undisclosed price.

Employees of Alliant, which is based in Newport Beach, California, own 45 percent of the company and will roll over a “substantial” amount of their investment in the company under KKR’s ownership, the companies said in a statement.

“This transaction will enable Alliant to remain independent and maintain its market leading position,” Tom Corbett, the company’s chief executive officer, said in the statement.

Private-equity firms are buying insurance-services companies for their steady cash flow and low capital expenditures. A group led by CVC Capital Partners Ltd. agreed last month to buy insurance-claim adjuster Cunningham Lindsey Group Ltd. in a deal valuing the company at as much as $1 billion including debt.

New York-based Blackstone, the world’s largest manager of alternative assets such as private equity, real estate and hedge funds, is exiting Alliant five years after buying it in 2007 for an undisclosed amount at the height of the buyout boom.

JPMorgan Chase & Co. advised Blackstone and Alliant on today’s deal, which is expected to close by the end of the year.