[Thumper]

Yep, this is an easy fix. It looks as if the bolt just came loose. I would go ahead and wiggle the bolt to get the head to clear the firewall and remove it with the ider pulley so you can check the idler pulley bearing. If it still rotates smooth, then put it back together, tighten the bolt and reinstall the serpentine belt. If the bearing seems loose, I'd go down and buy another one from the stealership.

I just did this on mine a couple of weeks ago, but my problem was the water outlet cover that the alternator attaches to broke off. So I had to replace the water outlet cover and while I was at it, I replaced the tensioner pulley and the two idler pulleys. A new serpentine belt, a little antifreeze and I was back in business. I don't know how old your serpentine belt is, but if it were me, I'd put the new one on anyway and keep the old one as an emergency belt.