Bernard J. Tyson, the chairman and chief executive of Kaiser Permanente, the large and influential California health care organization that many view as a model for the rest of the country, died on Sunday. He was 60.

In a statement, the company said he had unexpectedly died in his sleep but gave no other details.

Mr. Tyson had worked for Kaiser Permanente, which is based in Oakland, for more than three decades, beginning in the medical records department. He later became a hospital administrator and held a series of executive posts with the company until being named chief executive in 2013 and chairman the year after that.

Kaiser’s board of directors said Gregory A. Adams, executive vice president and group president, would serve as interim chairman and chief executive.

By the time Mr. Tyson took it over, Kaiser, founded in 1945, had evolved from a classic health maintenance organization, or H.M.O., into one of the most respected health care groups in the United States, combining a network of hospitals and clinics with its own nonprofit health plan, in which its doctors track patients closely. With its holistic approach, Kaiser built a reputation for providing consistent high-quality care.