Moving to Idaho at the absolute coldest time of year... wow.
Okay let me help you out.
First off, staying warm is not necessarily about thickness of material. It is about keeping a bubble of warm air around you. So the first part of that is going to be a thin layer of skin-tight, breathable, insulating material. This is called the base layer. The best quality is from fine wools, either merino wool or sometimes alpaca. When you see these can easily be over $100 for just a top or bottom you might think it is a joke, but it is not and they are very important, actually. You can get some made from synthetic materials that are pretty good, but the comfort is lower and imo they can kind of smell with your sweat. Up to you. For synthetics Patagonia, Marmot, Columbia, Outdoor Research, Arc'teryx are good brands.
Second part is the shell. This is usually where you see the big puffy coat comes in and it can be puffy if you want but doesn't really need to be all that bulky. The important thing is being windproof both in terms of the material wall and in sealing off ways the cold air can blow in. This means elastic bands, sometimes pulls to cinch things down on you, etc. The brands mentioned above all have great options with well insulating materials. I have a Canada Goose coat, which I do think is the best but it appears to have tripled in price since I got it, so I'd look at other brands.
Having the baselayer being of this more neutrally-insulating material will allow you to shed the hyper-warm shell once inside and not feel too warm. Most people want to neglect going to too much trouble to keep their legs warm, but I would strongly suggest you not neglect that. Yeah, maybe you don't need to have shell pants, particularly if you have a long coat, but do not neglect your baselayer on the legs.
For gloves I think it's a good idea to get some goretex-shielded half-finger gloves which you wear more serious gloves over. In Illinois I actually had some mittens that let the top flip back when you needed your fingers for a moment. That was nice. For socks I would strongly, strongly recommend just high quality wool, not overly bulky acrylic options. If you feel like you need super thick socks, you didn't pick the right boots and the socks will never make up for that bad choice.
Speaking of boots, they make these things that are kind of like sandals for your boots that strap on with velcro and they have little hex head screws that screw into the bottom to function like cleats. Most of the time you shouldn't need to resort to something so dramatic and dorky but if you have some on hand when the 5 inch ice storm hits, no one will be laughing at you being able to easily walk around and handle your shit when no one else can.
You want proper protection for your head and face. You lose tons of heat through your head and most people neglect proper gear. In keeping with the general principle, an insulating layer with windproofing shell is key. A single acrylic hat isn't going to do shit. I would go with a nice thin microfleece with a high thermal rating then a larger insulated hood. Now, when the weather gets to 0 and below and gets windy, you'll find it hurts to breathe and even kind of pulls your breath away from you. Just covering with a scarf or mask kind of just stifles your breath even more and also absorbs the moisture of your breath to get both gross and cold. To remedy this you can get something called a Cold Avenger mask. Just google it, their impact is amazing.
At those super low temperatures you'll also find that the wind causes a stabbing pain in your eyes. My first recommendation would be to get a better hood, as it should be able to cut the wind to blow across in front of them, but if the situation is really drastic, a step below ski goggles would be Oakley sunglasses. They come in nice shapes that cover a lot of area and seal around the eye decently. They also have by far the best protective films I've seen to enhance contrast and visibility in whiteout conditions and reduce eyestrain. Just make sure the ones you're looking at are specifically for skiing/snowboarding.
Health things:
-Get really good lighting in your place. The incredible lack of sunlight in the winter is very depressing. This can be countered with nice quality light in your home. Don't use dim bulbs with poor color. Also, one of those alarm clocks with an increasing light can really help in the morning.
-Make sure to drink enough water. Many people drink less in the cold and dehydration is the biggest contributing factor to being susceptible to the flu and such.
-Especially coming from Florida, you may want a humidifier for your place. The extreme cold portion of winter dries everything out.
