America bid farewell to one of the biggest hits in television history last night, with Fox’s “American Idol” attracting its largest audience in a couple of years and its biggest finale audience in three years.

More reliable Nielsen numbers will be available in a few hours, but the star-studded, 126-minute “Idol” finale averaged a 3.0 rating/10 share in adults 18-49 and 12.9 million viewers overall from 8 to 10 p.m. last night, with these averages expected to rise once the final six minutes are included. Given that the final half-hour averaged a 3.4 in the demo and 14.5 million viewers, it’s likely that its average for the night will finish in the vicinity of 13.4 million.

Prior to last night, the show’s season peak came with its premiere on Jan. 6, which did a 3.0 in 18-49 and about 11 million total viewers. The show had averaged about a 2.3 same-day rating and 10.5 million total viewers on Wednesdays and Thursdays this season.

Among all telecasts, the grand finale of “American Idol,” which included appearances and performances by numerous alums as well as the return of creator Simon Cowell, could stand as the show’s most-watched since early in season 13. That year’s premiere drew 15.2 million viewers, and a few other episodes topped 13 million.

Among “American Idol” finales, last night appears to be the most-watched in three years — since season 12 wrapped with 14.3 million.

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Dubbed during its heyday by Fox’s network rivals as “the Death Star” because it demolished everything in its path, “American Idol” peaked in 2006 and 2007 with about 30 million viewers nightly. It was so popular during the mid-aughts that several season premieres and finales even out-rated the Oscars.

Fox decided to pull the plug on the series after a stretch of double-digit ratings declines in recent years. Still, despite the falloff, “American Idol” remains the network’s No. 2-rated series, behind only “Empire,” and the network’s top execs know the near future could be challenging.

Elsewhere Thursday, CBS’ “The Big Bang Theory” was the top-rated alternative, and its 3.0 rating/11 share in adults 18-49 and 13.2 million viewers overall figures to finish a bit behind the final “Idol” numbers. The comedy did easily beat “Idol” head-to-head (roughly 3.0 to 2.4 in 18-49 and 13.2 million to 10.8 million in total viewers), but these represent season lows for the show.

It was followed by the second-season premiere of “The Odd Couple” (1.6/6 in 18-49, 7.8 million viewers overall), which appears to have retained about half of the “Big Bang” young-adult audience in its tough task of opening against “Idol,” which grew with each half-hour. It was followed by “Mom” (1.5/5 in 18-49, 7.3 million viewers overall) and “2 Broke Girls” (1.4/5 in 18-49, 5.9 million viewers overall), both of which were down multiple tenths from last week. And at 10 p.m., “Rush Hour” (0.9/3 in 18-49, 4.8 million viewers overall) was down 0.2 in its second week.

ABC had a good night with its dramas, starting with “Grey’s Anatomy” (2.1/8 in 18-49, 7.3 million viewers overall), which was down just a tenth from last week. It grew week to week by 12% in adults 18-34 (1.9 from 1.7) to hit an eight-week high, while growing for a fourth straight week in women 18-34 to its best rating since early November (2.8/12).

“Scandal” (1.7/6 in 18-49, 5.9 million viewers overall) held even to match a six-week high — a positive sign given the tough “Idol” competition and the return to original episodes for NBC’s “The Blacklist.” It beat the Peacock drama by 42% in 18-49 (1.7 to 1.2).

And at 10 p.m., “The Catch” (1.1/4 in 18-49, 4.9 million viewers overall) moved up to No. 1 for the hour, rising a tenth from last week and improving upon “American Crime” in the hour a year ago by 22% (0.9). In “live plus-3,” last week’s episode grew by 0.68 (or 66%) in 18-49 rating from its same-day average (1.03), leaving it down 10% from its premiere (1.89) after lagging in same-day numbers by 16% (1.03 vs. 1.22).

NBC sandwiched the return of “The Blacklist” (1.2/4 in 18-49, 6.2 million viewers overall) with special off-night encores of “Little Big Shots” (0.8/3 in 18-49, 4.5 million viewers overall) and “Law & Order: SVU” (0.8/3 in 18-49, 3.9 million viewers overall). The James Spader drama

At CW, “DC’s Legends of Tomorrow” (0.7/3 in 18-49, 2.0 million viewers overall) held steady, while “The 100” edged up (0.5/2 in 18-49, 1.3 million viewers overall).