Another two-hour edition of “American Idol” dominated Wednesday’s primetime ratings action as Fox beat ABC, CBS and NBC combined in demos. Also, CBS’ “Criminal Minds,” ABC’s “Modern Family” and NBC’s “Law & Order: SVU” all gave their nets something to be happy about.

According to preliminary nationals from Nielsen, “American Idol” averaged a big 8.5 rating/23 share in adults 18-49 and 23.5 million viewers overall from 8 to 10 p.m., logging its best demo share (24) and largest total audience (24.5 million) in the 8:30 half-hour. The music talent show was roughly on par with last week but dipped about 7% in 18-49 vs. the comparable night a year ago. Season to date, “Idol” is running about 5% behind last year’s pace.

CBS ran a distant second, starting slowly with “The New Adventures of Old Christine” (1.7/5 in 18-49, 6.0 million viewers overall) and “Gary Unmarried” (2.0/5 in 18-49, 6.0 million viewers overall) before picking up steam with “Criminal Minds” (3.6/9 in 18-49, 13.2 million viewers overall) and “CSI: NY” (3.1/9 in 18-49, 12.5 million viewers overall). “Minds” was the night’s No. 2 program in most categories, and “CSI: NY” narrowly won its hour in 18-49 while prevailing by larger margins in 25-54 and total viewers.

NBC improved its fortunes markedly from 9 to 11 p.m. by going with a two-hour episode of “Law & Order: Special Victims Unit” (2.7/7 in 18-49, 8.3 million viewers overall), which logged its best scores since mid-November. In what is now its new timeslot at 10 p.m., “SVU” roughly doubled the net’s season-to-date timeslot average and finished neck and neck with “CSI: NY” for the 18-49 lead. Opening the night, first-year nurses drama “Mercy” (1.6/5 in 18-49, 6.0 million viewers overall) was in line with its recent averages.

At ABC, “Modern Family” continues to perform well at 9 p.m. (3.5/9 in 18-49, 8.1 million viewers overall) even in the face of “American Idol.” It edged past “Criminal Minds” for second place in 18-49 and helped prop up a night for the net that otherwise saw mediocre numbers. Following a “Modern Family” repeat at 8 (1.7/5 in 18-49, 5.2 million viewers overall), “The Middle” (2.1/6 in 18-49, 6.0 million viewers overall) scored a narrow second-place demo finish. And after “Family,” “Cougar Town” dropped off to a 2.4/6 in 18-49 and 5.4 million viewers overall, followed by a weak-performing “Oprah Winfrey Oscar Special” (1.3/4 in 18-49, 4.4 million viewers overall).

Preliminary 18-49 averages for the night: Fox, 8.5/23; CBS, 2.8/8; NBC, 2.3/6; ABC, 2.0/6; Univision, 1.3/4; CW, 0.3/1.

In total viewers: Fox, 23.5 million; CBS, 10.5 million; NBC, 7.5 million; ABC, 5.6 million; Univision, 3.3 million; CW, 0.7 million.