The Bengals (9-10, 4-3 Big Sky Conference) shot 60 percent on 28-of-47 shooting from the floor, and made 10 of 18 3-pointers (57 percent).
Telfair made 5 of 10 field goals and all eight free-throw attempts. Geno Luzcando had 16 points and Ben Wilson 14 for the Bengals. Clint Nwosuh had three 3-pointers and finished with 13 points, and Gary Chivichyan added 12 points on 4-of-6 shooting from beyond the arc.
James McGee scored 17 points for Southern Utah (4-14, 2-6).
The Bengals jumped out on a 20-8 run before McGee scored nine points and Race Parsons made a 3 to pull the Thunderbirds to 29-20. Telfair answered with a jumper and Idaho State led by double digits the rest of the way.