Mariah Carey and Nicki Minaj have quit 'American Idol'. 43-year-old singer Mariah Carey has confirmed she will leave the show after just one season in order to undertake a world tour following the success of her latest single 'Beautiful'.'Starships' singer Nicki Minaj has followed in the footsteps of Mariah by confirming her first season on the show will also be her last.Nicki wrote on Twitter: "Thank you American Idol for a life changing experience! Wouldn't trade it for the world! Time to focus on the Music!!! Mmmuuuaahhh!!! (sic)."Mariah retweeted a message from her PR representatives which read: "W/ global success of "#Beautiful" (#1 in 30+ countries so far) @MariahCarey confirms world tour & says goodbye 2 Idol http://mariahcarey.com (sic)."Randy Jackson, who was the only original judge remaining on the show recently revealed he made the decision not to return next season because he wants to focus on his other interests.He said: "Yo! Yo! Yo! To put all of the speculation to the rest, after 12 years of judging on American Idol I have decided it is time to leave after this season," he says. "I am very proud of how we forever changed television and the music industry. It's been a life changing opportunity but I am looking forward to focusing on my company Dream Merchant 21 and, other business ventures."Keith Urban is the only remaining judge on the show, and it is unclear if he will return next season.