UnitedHealth Group’s stock fell Thursday after the company confirmed government criminal and civil investigations into its Medicare practices but stressed that it doesn’t expect to be charged with any wrongdoing.

Once considered a reliable bet, the health care behemoth has lost its appeal following a series of management missteps. UnitedHealth’s stock has fallen more than 40% so far this year. Independent CMS audits confirm that UnitedHealth’s practices are among the most accurate in the industry, the company said.