What skis do you have right now? Are they in need of replacement or will you still use them? If you already have on-piste oriented skis I would recommend keeping those for the days when the conditions suck and getting some big pow skis for the good days.
Snowbird is my home ski area and my daily drivers are 117mm. I use them pretty much always, I only take out my narrower skis if it's been hot and no snow for a long time. That said, a lot of people prefer something a bit narrower for a daily driver. I tend to like wide skis.
If you really are looking for a ski primarily for powder and off-piste in general, I would recommend getting something about that size, just know that they will be far from ideal when the conditions suck. It also depends on how good of a skier you are. While big pow skis are not ideal for anyone when the conditions suck, expert skiers will have no problem making do with them, but beginners and intermediates will find them next to impossible to control on the worst days.
If you don't mind having less than ideal skis when the conditions suck, or if you already have a pair of narrower skis you can continue to use, I would recommend going around 115mm-120mm+ waist. Some models to consider are the Pettitor, Bent Chetler, Shiro, New Life, JJ, etc. If you want to spend a lot of time in the trees you'll probably want something with a relatively short turn radius such as the JJ, if you mostly want to ski more open areas and charge hard through pow and chop you'll want something more like the Pettitor or Bent Chetler.
That said, all of those skis (really pretty much any ski you'll find that's that wide and pow oriented) are designed for advanced and expert skiers. If you want something a bit more intermediate-oriented, and better on groomed runs and bad snow conditions, look more at skis in the low 100s (100mm-112mm). I am not as knowledgable in that area as I almost always ride fatter skis, so others could probably make better suggestions in this area, but some I would recommend looking into are the Atomic Vantage Ritual and Shreditor 102 or 112. While these skis will be easier to handle and better for variable conditions and groomers, they will not have as much float in pow as the wider skis I recommended and won't be as good for charging hard off-piste when the conditions are good.
Give us a little more info on you--whether you have on piste skis you can continue to use, whether or not on-piste performance matters to you, how much you'll be skiing trees and bumps versus more open areas, how agressively you ski, etc. Also, where did you ski in the past? When you said you ski pretty much any blue run, you mean in Utah or where you used to ski? It makes a big difference, I have skied double blacks that were easier than one of Snowbird's greens.