Justin Burrell #24 and Paris Horne #23 of the St. John's Red Storm fight for position against Robert Sacre #00 of the Gonzaga Bulldogs - March 17, 2011

The first day of March Madness drew the highest ratings for the NCAA basketball championships in 20 years, according to CBS Sports and Turner Sports.

The games — broadcast on CBS, TNT, TruTV and TBS — earned a combined 5.7 overnight rating, the highest since 1991 and up 24 percent from last year's debut.

See the full March Madness TV schedule

Thanks to the new CBS Sports and Turner Sports deal, all the second-round games were aired in their entirety for the first time this year. All four telecast windows of the day saw increases, with the biggest being a 46 percent year-to-year growth for the second window (3:00-6:45 p.m./ET).

In prime time, CBS averaged 4.7 million viewers for its coverage of two games, bringing the network to a third place finish for St. Patrick's Day.

Fox won the night, buoyed by American Idol, but the 19 million viewers who tuned in to the show marked a season low and a 16 percent drop from last week. Bones, however, was up 13 percent, drawing 11.9 million viewers for an episode directed by David Boreanaz.

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ABC came in second place with Winter Wipeout (7.1 million), Private Practice (a series low of 6.1 million viewers) and Off the Map (4.1 million).

NBC placed fourth with season lows across the board: Community (4.2 million), Perfect Couples (2.9 million), Parks and Recreation (4.4 million), 30 Rock (4.4 million) and Outsourced (3.9 million). An Office repeat garnered around 4 million.