Brian D. Pieninck plans to step down as president and CEO of Maryland’s largest insurance company, CareFirst BlueCross BlueShield, and take over a Florida health insurance company that is parent to other nonprofit health plans.

GuideWell Mutual Holding Corp. announced Monday the appointment of Pieninck as its next president and CEO, effective Oct. 1. GuideWell’s subsidiaries include Florida Blue and Triple-S Salud, the BlueCross BlueShield plan for Puerto Rico.

A decade ago, Pieninck began his CareFirst career as an executive vice president and became chief operating officer in 2017, taking over the top job a year later. CareFirst serves about 3.5 million customers in Maryland, Washington, D.C. and Virginia. GuideWell serves about 38 million.

Pieninck will leave his Maryland post in September. Ja’Ron Bridges, CareFirst executive vice president and chief financial officer, will serve as interim chief executive officer while the board begins a search for a permanent successor, according to a statement from CareFirst.

The statement characterized Pieninck’s tenure as one of significant growth, diversification and modernization. CareFrist expanded into Medicare and Medicaid coverage and expanded access to primary and urgent care.

Bridges will face some uncertainty in the state’s health care landscape, particularly as federal cuts to Medicaid could mean some consumers lose coverage and others pay more in Maryland and elsewhere. The industry also is coping with frustration at medical costs and coverage generally.

“The organization is well positioned to move forward with purpose—staying grounded in our mission, accelerating innovation and continuing to improve access and the overall health of the communities we serve,” Dr. Jeffrey P. DiLisi, CareFirst board chair, said in a statement praising Pieninck’s tenure.