Fast National ratings for Thursday, April 7, 2011.
 
"American Idol" delivered another big results surprise on Thursday night to its smallest audience since the time shift drop last month. Meanwhile, "Bones" delivered a smaller demo number than last week's "Mobbed" special. Negatives aside, FOX still scored comfortable wins on Thursday night.
 
Among adults 18-49, FOX averaged a 4.8 rating for the night, easily tops in the coveted demographic. CBS was second with a 2.9 rating, far ahead of the 1.3 rating for NBC, the 1.2 rating for ABC and The CW's competitive 1.0 rating.
 
Overall, FOX averaged an estimated 15.96 million viewers and a 9.3 rating/15 share, beating the 12.41 million viewers and 7.8/13 for CBS. There was a big drop to ABC in third with 3.86 million viewers and a 2.6/4. NBC averaged a 1.8/3 and 2.765 million viewers to barely hold off the 1.5/2 and 2.26 million for The CW.
 
8 p.m. - "American Idol" ruled the 8 p.m. hour with 20.65 million viewers and a 6.1 rating among adults 18-49, way down from last week. CBS was second with "The Big Bang Theory" (11.24 million viewers and a 3.6 demo rating) and "Rules of Engagement" (8.61 million and a 2.5 demo). ABC's repeat of "Wipeout" was third with 5.1 million viewers. The CW -- yes, The CW -- leapt up into fourth with 2.75 million viewers and a 1.2 demo rating for the return of "The Vampire Diaries." That meant NBC was fifth with a repeat of "Community" and a new "Perfect Couples" averaging 2.28 million viewers and a 0.9 demo rating.
 
9 p.m. - CBS moved into first overall in the 9 p.m. hour with 12.61 million viewers, taking second in the key demo with a 2.8 rating. FOX's "Bones" averaged 11.28 million viewers for second overall and a 3.4 demo rating to win the hour, delivering more viewers, but a lower demo than "Mobbed." ABC's "Grey's Anatomy" repeat averaged 4.02 million viewers, better than the 3.23 million for NBC's repeats of "The Office" and "Parks and Recreation." The CW's "Nikita" averaged 1.78 million viewers and a 0.7 demo rating, taking a big drop from its lead-in.
 
10 p.m. - "The Mentalist" closed primetime in first for CBS with 14.68 million viewers and a 2.9 demo rating. NBC's repeat of "30 Rock" and a new "Outsourced" averaged 2.78 million viewers to nip the 2.46 million viewers for ABC's "Private Practice." 
 
All ratings information comes from preliminary Fast National Nielsen data, which includes live and same-day DVR viewing. All numbers are subject to change.