A Ratings Uptick for 'Idol' February 10, 2012, 4:13 pm The ratings for "American Idol" reversed their course on Thursday night, growing slightly compared to last week, which provided Fox with a win for the night in the 18-to-49-year-old demographic coveted by advertisers. CBS drew the most viewers over all. An average of 17.9 million people watched "Idol," barely beating last week's total of 17.4 million but the show was also up 4 percent in the 18-to-49 category. Again, not a large gain, but a change from the downward trend that followed earlier episodes. The CBS lineup continued its strong performance as "The Big Bang Theory" drew 16.1 million total viewers and beat "Idol" with adults 18-to-49 in the half-hour they went head to head, while "The Mentalist" had its largest audience of the season with 14.4 million viewers.