Fox said in July that pop singer Mariah Carey would join the panel, while the network also confirmed Sunday that veteran judge Randy Jackson would return. The new additions follows news earlier in the summer that last season judges Jennifer Lopez and Steven Tyler were departing.
Minaj is the top female rapper in a hip-hop world dominated by male artists. She burst onto the music scene in 2010 and quickly made a name for herself by adopting numerous alter-egos and with multiple hit records. She has also proved controversial, appearing on the Grammy awards red carpet in February with a fake pope. She made headlines last week for expletive-filled lyrics that appeared to support U.S. Republican contender Mitt Romney.
Urban has four Grammy Awards and 14 No. 1 hits, and was named Male Vocal Artist of the Year three times, as well as Entertainer of the Year, by the Country Music Association.
The addition of Minaj could add an element of unpredictability to draw younger viewers. Audiences are now only about half the more than 30 million who watched regularly in the show's 2005 and 2006 seasons. The last season finale in May drew a record low of 21.5 million viewers and "Idol" lost its eight-year crowd.
Minaj is expected to receive about $8 million and Urban will get around $4 million.