OPERATING LEASES (Details) $ in Thousands	1 Months Ended							12 Months Ended
	Dec. 31, 2013 item	May 31, 2013	Sep. 30, 2012 item	Feb. 28, 2011	Apr. 30, 2010 item	Apr. 30, 2008	Sep. 30, 2005	Dec. 31, 2017 USD ($) item	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014	Dec. 31, 2011
OPERATING LEASES
Number of operating leases | item								7
Additional number of operating leases acquired | item								3
Future minimum payments, by year and in the aggregate, under the initial terms of the operating lease agreements
2018								$ 772
2019								747
2020								608
2021								503
2022								499
Thereafter								3,124
Total								6,253
Rent Expenses
Rent expense for all operating leases								$ 1,109	$ 1,053	$ 985
Birmingham
OPERATING LEASES
Operating lease term							66 months
Option to renew additional lease term							5 years
Additional period for operating lease								3 years			3 years	3 years
Manistique
OPERATING LEASES
Additional period for operating lease					2 years
Maximum number of additional lease terms for which the lease may be extended | item					4
Traverse City
OPERATING LEASES
Operating lease term								36 months
Option to renew additional lease term								36 months
Maximum number of additional lease terms for which the lease may be extended | item								2
Marquette
OPERATING LEASES
Operating lease term	15 years			5 years
Additional period for operating lease	4 years
Maximum number of additional lease terms for which the lease may be extended | item	2
Negaunee
OPERATING LEASES
Operating lease term			5 years
Additional period for operating lease			5 years
Maximum number of additional lease terms for which the lease may be extended | item			1
Ishpeming
OPERATING LEASES
Operating lease term						5 years
Option to renew additional lease term		5 years