Detroit has rarely been kinda to United flyers and the big 4 michigan airports are all lacking attractive long distance mileage running options.
If you're looking for an excuse to get away, US has DTW-PHL/CLT/PHX-LAS for 240RT. Probably is going to be the closest to a true mileage run fare right now. I realize you only need a few miles but I wanted to offer you an option for only a little more than what others were offering to have a bit of fun.