As Fox News finally showed Bill O’Reilly the door late last week, managers everywhere winced in sympathy. Many have lived through the realization that they have hired, inherited, or created a toxic but high-performing employee. Businesses value superstar employees so much that they often turn a blind eye to toxic behavior—but this is a mistake, and can end up damaging both a company's reputation and its wallet. Ultimately, it's a manager's job to take control and curb toxic behavior as early and as quickly as possible.