Detroit. MI to Denver, CO (where you're not yet in the mountains) is 1,270 miles (2,044 km), 19 hours' driving time assuming excellent driving conditions and not including any stops. You can get this information from Mapquest or Google.
Watch the weather forecasts carefully. We do have blizzards in winter which sometimes close highways for many hours, or at least force you to drive well below the speed limit.
In other words, flying is a far better idea!
Although not as spectacular as the Rockies, Michigan has plenty of downhill and nordic skiing and interesting places to backpack.