LOS ANGELES (Reuters) – The audience for "American Idol" slumped 19 percent to 17.9 million viewers, its lowest season opener, despite the debut of judges Mariah Carey, Nicki Minaj and Keith Urban, according to early ratings data released on Thursday. The two-hour premiere of the show's 12th season on Fox television also lost 19 percent of the 18-49 age group most coveted by advertisers, Nielsen figures showed. Total viewers dropped to 17.9 million from 21.9 million in 2012. Despite the drop, "American Idol" was still the most watched show by a huge margin on U.S. …
