Zurich U.S. has selected Alex Wells to serve as chief executive officer. He takes the helm from Sierra Signorelli, who stepped down.

The promotion takes immediate effect but is still subject to customary approvals.

Wells previously served as president of Zurich U.S. Middle Market, Programs, Captives and Direct Markets, which together comprise the largest business within Zurich U.S. This role included serving on the Zurich U.S. Executive Committee. He is a veteran insurance executive with over 25 years of experience, including senior leadership roles in commercial insurance for Chubb and ACE.

Mario Greco, group CEO of Zurich Insurance Group, said that Wells “has a strong track record of delivering results, developing talent and helping teams perform at their best. His appointment positions us to build on the progress made in recent years.”

Greco added: “We thank Sierra for her contribution and commitment during her time with us and wish her all the best in her future endeavors.”

Pending approval of the CEO appointment, Wells will be based at Zurich U.S. headquarters in Schaumburg, Illinois.

Zurich also announced that John Diaz has been appointed to succeed Wells as president of U.S. Middle Market, Programs, Direct Markets and Captives, effective immediately.

Diaz will maintain his role as president of Customer & Distribution Management until a successor is named.

He joined Zurich in 2008 and has held a series of executive leadership roles across the organization, including a previous stint in Zurich’s U.S. Middle Market business as head of Underwriting, and before that as chief operating officer.