Simon Cowell makes it official. Says this is his last year on 'Idol.'

Simon Cowell made it official today, telling the TV critics at the TCA Press Tour that he is leaving 'American Idol' after this season.

Cowell signed a contract with Fox today to judge 'The X Factor' beginning next year. "I didn't think it was right for me to do two shows in America," Cowell said. He also said he felt it would be impossible to do both shows.

Now things could change here. 'X Factor' and 'Idol' are scheduled to run at different times during the year and since they are both on Fox, there's no reason that Cowell couldn't do both. This could just be part of a negotiating ploy.

Fox execs said that they wouldn't speculate on a replacement for Simon.