Simon Cowell, the lovably cantankerous music expert, is officially leaving 'American Idol' after this current season. The biggest star on TV's biggest show will depart in 2011 to begin his role as the face of 'The X Factor,' the show he created in Britain that he has plans to make a hit in the States. FOX will air 'Factor' as well, so Cowell is staying on the network.

Cowell and top Fox executives made the announcement to reporters in Pasadena at a meeting of the Television Critics Association, saying they had reached an agreement only a few hours before.

"I was offered a lot of money to stay on," Cowell said. "But that wasn't the reason behind it. I wanted to do something different. I wanted a new challenge."