There are many types of mint plant (chocolate mint is one of my favorites) but most all are hardy in your area. You can cut it back by one half now in early winter then the remaining leaves can help protect the roots from the winter cold. In spring you can cut the overly enthusiastic mints back to just a few inches and you will still have lots of spreading green growth in just a few weeks. If it is really cold or rainy move the container close to the house under the eaves a bit for added protection and so that the rains do not drown the plant - mints do love moisture however so don't let the pot dry out. Keep harvesting the fresh mint leaves all winter to add to teas another foods. This herb is good for you! In a year or so the mint plant will fill the pot with roots. That is when you can divide up the plant and add some fresh potting soil. Make the divisions in  the spring and you'll have fresh mint all summer and into the fall. Perhaps you'll muddle that fresh mint into Mojitos -  cheers! Keep growing, Marianne Binetti