First off, the guy made an ok call i'd say. He was defending his blinds, and his run, with a pretty decent hand. What can be questioned here is not only his call but your shove. AT shoves 18bb's into 15bb's? I wouldn't. With 18 bb's surely I would be opening here but for me I wouldn't be open shoving. We're not short stacked. Open raise and see what ya get. If he pushes back, possibly fold. If he calls and the flop misses me, I save my whole stack and fold
Assuming neither are suited, you're about a 60/40 favorite. You have not connected anything thus far. You will lose 2 of every 5 times. Just my .02 cents