Doing a few estimates if the tower is 18 floors, it will still be the new tallest. The fact that the first level is retail and the rest of the base is parking, I come up with a 280' tower at 18 floors. At 20 floors it comes out to 308'. 17 floors comes out to 267'. The very minimum at 15 floors is 240'.
All in all, no matter how many floors the developers decide on, the Boise skyline will drastically change with the addition of this tower.