Hallam was 6 of 8 from the floor. Royce O'Neale chipped in eight points, six assists and five rebounds for the Pioneers (8-7, 4-1 Western Athletic), who closed the game on an 8-1 run.
Mike McChristian put Idaho ahead 48-47 on a layup with 1:35 to play, but Hallam's layup with 1:14 left gave Denver the lead back before Brett Olson, Cam Griffin and O'Neale each made two free throws to seal the victory.
Denver also won its only other games against Idaho, in 1965 and 1966.
Kendrick Nunn, who pleaded guilty to misdemeanor domestic battery last week, has been dismissed from the Illinois basketball team.
Delaware has hired Notre Dame assistant Martin Ingelsby as its next men's basketball head coach, sources told ESPN's Jeff Borzello.
Michigan State-Duke in the ACC/Big Ten Challenge will pit two of the best recruiting classes in the nation. Here's a look at all the games.