U.S. private equity firm Insignia Capital Group has agreed to acquire a significant minority stake in MediaAlpha, a digital advertising unit of Bermuda-based insurer White Mountains Insurance Group Ltd.

White Mountains expects to receive net cash proceeds of approximately $85 million from the transaction.

The deal will close within 60 days, subject to the satisfaction of customary closing conditions and MediaAlpha securing new third-party debt financing of approximately $100 million.

MediaAlpha expects to use the proceeds to effect a dividend recapitalization. As a result of the deal, White Mountains will remain with a 42 percent ownership interest in MediaAlpha.