Pittsburgh-based health care insurer Highmark is adding more than 1 million members to its base, through a proposed affiliation with Blue Cross and Blue Shield of Kansas City.

The affiliation will aim to accelerate innovation and improve health outcomes for members, according to a Highmark news release. The deal is subject to regulatory approvals and customary closing conditions.

Highmark and its Blue-branded affiliates collectively comprise the fifth-largest overall Blue Cross Blue Shield-affiliated organization in the country, with more than seven million members in Pennsylvania, Delaware, West Virginia and western and northeastern New York.

Together, the two not-for-profit health insurers will serve nearly eight million members nationwide.