Chicago is the closest city with a Chanel boutique.
Other than that, the Sommerset Collection mall in Troy MI has a Neiman Marcus and Saks that both have a Chanel location inside them. It's about a 30 minute drive from the Detroit airport. There are no other Chanel locations in MI. You might want to call in advance to see if they have what you are looking for or to see if they can get what you want.
Diane is the Chanel specialist at the Troy Saks and Jennifer is the Chanel specialist at NM. Lisa and Barbara at NM are also great and can find almost anything. If there is something you want but don't see ask b/c Jennifer does not keep every style or color out on the floor. NM usually has the largest selection, also check the third floor for bags that are on display in the Chanel RTW area.