CBS controlled the second Thursday of the February sweep as “The Big Bang Theory” grew and opened up a huge advantage over Fox’s declining “American Idol.”

ABC’s drama block remained potent, with “Scandal” matching a series high and winning among young adults at 10, while NBC saw solid premiere scores for “Community,” but it was very slow going for the Peacock closing out the night with newcomers “1600 Penn” and “Do No Harm.”

According to preliminary national estimates from Nielsen, “The Big Bang Theory” was easily Thursday’s — and more than likely the week’s — top program in key demos (6.1/18 in adults 18-49, 7.8/20 in adults 25-54) while drawing 18.8 million viewers overall. It was up from the show’s below-average delivery of the previous week, besting “American Idol” by 61% in 18-49 (6.1 vs. 3.8) after that advantage had been 29% one week earlier.

Following “Big Bang,” “Two and a Half Men” was up a bit at 8:30 p.m. (4.1/11 in 18-49, 14.1 million viewers overall), placing second to “American Idol” in 18-49. “Person of Interest” held steady at 9 (3.2/8 in 18-49, 15.2 million viewers overall), winning in demos and dominating in total viewers, and “Elementary” edged up at 10 (2.3/6 in 18-49, 11.0 million viewers overall) four days after its special post-Super Bowl episode.

At Fox, “American Idol” (4.1/12 in 18-49, 13.2 million viewers overall) was down 9% week to week to a season low but still tied with “Two and a Half Men” as the night’s No. 2 show in 18-49. Despite that dip, “Glee” edged up at 9 (2.2/6 in 18-49, 6.1 million viewers overall) and ran a close second to “Grey’s Anatomy” among persons 12-34 (2.0/7).

ABC was up a bit at 8 p.m., but remained out of the competitive loop, with a special repeat of “Shark Tank” (1.3/4 in 18-49, 4.8 million viewers overall). It picked up steam, though, at 9 with “Grey’s Anatomy” (3.1/8 in 18-49, 8.8 million viewers overall), which bounced back from a sub-par outing last week to nearly catch “Person of Interest” in 18-49. And at 10, “Scandal” (2.8/8 in 18-49, 8.0 million viewers overall) was up a tick from last week to match its series high, winning the hour in 18-49; the sophomore drama has now posted its six best 18-49 scores with its last six original episodes.

NBC had a pretty good first half of the night, but not so much in the second half. “Community” returned with a 1.8/6 in 18-49 and 4.0 million viewers overall in the 8 o’clock half-hour — up a tick from its premiere of last season (in September), and beating out Fox’s “American Idol” in men 18-34 for the first time. “Parks and Recreation” followed with its best scores since November 2011 (2.0/5 in 18-49, 3.8 million viewers overall), rising 18% from its most recent original; while it finished well behind “Two and a Half Men” in all broad categories, it did catch the CBS vet in women 18-34 (2.6/8).

But following steady anchor “The Office” at 9 (2.1/6 in 18-49, 4.3 million viewers overall), rookie half-hour “1600 Penn” hit a low at 9:30 (1.1/3 in 18-49, 2.8 million viewers overall). And in its second week, 10 p.m. drama “Do No Harm” (0.7/2 in 18-49, 2.2 million viewers overall) dropped a couple of ticks from its weak premiere score of last week.

At CW, “The Vampire Diaries” was on the low side (1.1/3 in 18-49, 2.5 million viewers overall), and “Beauty and the Beast” was down a bit as well (0.6/1 in 18-49, 1.5 million viewers overall)

Preliminary 18-49 averages for the night: CBS, 3.5/10; Fox, 3.1/9; ABC, 2.4/7; Univision, 1.7/5; NBC, 1.4/4; CW, 0.8/2.

In total viewers: CBS, 14.2 million; Fox, 9.6 million; ABC, 7.2 million; Univision, 4.0 million; NBC, 3.2 million.