“American Idol” led Fox to a Thursday victory in primetime, with “Grey’s Anatomy” nursing a second-place finish for ABC.

CBS, which has been sharing its March Madness college basketball audience with its Turner Sports broadcast partner this year, came in third.

While final numbers on basketball won’t be available until the afternoon, CBS said that the combined viewer totals of Thursday Sweet 16 games on CBS and TBS showed a 28% gain over CBS’ solo coverage compared with the same day in 2010, and that the 8.6/14 overnight household rating/share was the highest for this night of play since 1993.

“Idol” (6.2 rating/19 share among adults 18-49, 20.7 million viewers overall) had a week-to-week improvement of nearly 10% in the demo and dominated its 8 p.m. timeslot, whose runner-up was ABC’s “Wipeout” (2.3/7, 7.5 million). NBC comedies “Community”

(1.8/6, 4.5 million) and “Perfect Couples” (1.6/5, 3.4 million) were fourth in the hour, ahead of a repeat of the CW’s “Vampire Diaries” (0.5/1, 1.4 million).

“Perfect Couples,” which improved from a 1.2 demo rating the previous week, is scheduled to come off NBC’s schedule in mid-April to make way for “The Paul Reiser Show.”

At 9 p.m., “Grey’s Anatomy” (3.6/10, 10.1 million) got some demo competition in its first halfhour from NBC’s “The Office” (3.4/10, 7.1 million), which had been promoted as the episode in which Steve Carell’s Michael Scott would propose marriage. The Peacock’s “Parks and Recreation” (2.5/7, 5.2 million) performed well enough for NBC to hang onto third place for the hour in 18-49 ahead of Fox’s repeat of “Bones” (2.5/7, 8.8 million).

The CW’s 9 p.m. repeat of “Nikita” (0.5/1, 1.4 million) echoed its lead-in’s numbers.

Pending afternoon adjustments, CBS won the 10 p.m. hour with basketball, topping ABC’s “Private Practice” (2.7/7, 8.0 million). NBC’s “30 Rock” (2.0/6, 4.4 million) and “Outsourced” (1.5/4, 3.6 million) were third. NBC’s comedies all performed better than they had the previous weel.

Preliminary 18-49 averages for the night: Fox 4.4/13, ABC 2.9/8, CBS 2.5/7, NBC 2.1/6, Univision 1.7/5, CW 0.5/1.

In total viewers: Fox 14.5 million, ABC 8.5 million, CBS 7.2 million, NBC 4.7 million, Univision 4.2 million, CW 1.4 million.