Fox’s “American Idol” continues to slip in the ratings, based on Thursday’s Nielsen overnights. TVbytheNumbers.com reports that “Idol” delivered a 5.6 average rating in the key 18-49 demo, down 6% from a week ago. It was still easily the top show of the night, and Fox coasted to a big win for prime time overall.

Leading out from "Idol" on Fox, “Glee” returned with its first original episode since Dec. 13, surging 35% to a 2.7 average in 18-49.

The second-highest-rated show on the broadcast networks was a “Big Bang Theory” rerun on CBS, which delivered a 3.1 in viewers 18-49. CBS tied for second overall even while airing an all-repeat lineup.

ABC opened the night with the series finale of “Last Resort,” which “surged” 20% from last week to a still modest 1.2 rating in the 18-49 demo. “Grey’s Anatomy” led the network’s numbers with a 3.0, steady with a week ago.

NBC saw a now-typical soft turnout for its Thursday night lineup: a 1.4 average rating for “30 Rock” in viewers 18-49 (up 8% from last week); a 1.7 for “Parks and Recreation” (down 11%); a 2.0 for “The Office” (down 5%); a 1.3 for “1600 Penn” (up 8%); and a 0.8 for “Rock Center” (down 27%, tying the show’s season low).

For prime time overall, Fox led the way with a 3.9 average in 18-49, followed by ABC and CBS (both with 2.0 averages), Univision (1.6) and NBC (1.3). Total viewers was closer, with Fox on top with 11.2 million, followed by CBS with 9.3 million, ABC with 6.7 million, Univision with 4.0 million and NBC with 3.8 million.