Stephen Hemsley hasn’t been CEO at UnitedHealth Group in nearly a decade yet he’s never really left. Hemsley, 72, has remained chairman and a major shareholder in the health care behemoth — and now is back in the CEO

Stephen Hemsley ran UnitedHealth Group for more than a decade. It's a different company after four years with Andrew Witty in charge.

The Department of Justice has launched an investigation of UnitedHealth Group for possible criminal Medicare fraud, according to a new report.The investigation in connection to its Medicare Advantage business is in addition to

The reported probe adds to a string of recent setbacks that have erased more than half, or over $300 billion, from its market value since November.

UnitedHealthcare stock plunged again on Thursday after a new report in the WSJ said the company is facing a Medicare fraud probe.

Former CEO and current chairman Stephen Hemsley is stepping back into the top job following the abrupt resignation of Andrew Witty, UnitedHealth said.

UnitedHealth faces valuation reset amid CEO change, regulatory probes, and cost overruns. Click here for a full analysis of UNH stock.

As CEO for more than a decade, Stephen Hemsley built up UnitedHealth Group, now a $400 billion healthcare behemoth. With his return to the top job, the company will learn whether his playbook still works.