ALL’S FAIR: Geffen Chairman Ron Fair will join Interscope’s Jimmy Iovine with a full-time gig at American Idol when his deal is up this spring, according to sources. Fair will re-up with UMG for a new post that will see him devoting his energy to the Fox show, while still producing acts for the label. Ex-Sony A&R exec Larry Jackson was recently hired as EVP for Interscope Geffen A&M, and will take over some of his duties. Jackson was an A&R exec at J Records and RCA Music Group, working with Britney Spears, Jennifer Hudson and Alicia Keys. (1/21p)