BUSINESS COMBINATIONS (Details) $ in Thousands	1 Months Ended
	Aug. 31, 2016 USD ($) item	Apr. 30, 2016 USD ($)	Apr. 29, 2016 USD ($) item	Mar. 31, 2018 USD ($) shares	Jan. 16, 2018 USD ($)	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 USD ($)
Business Acquisition [Line Items]
Assets				$ 983,929		$ 985,367
Purchase Price:
Shares outstanding (in Shares) | shares				6,332,560		6,294,930
Net assets acquired:
Goodwill				$ 5,694		$ 5,694
Eagle River
Business Acquisition [Line Items]
Number of banking offices | item			3
Assets			$ 125,000
Purchase Price:
Total purchase price		$ 12,500
Net assets acquired:
Total Loans, net of purchase accounting marks		84,000
Deposit based intangible		933
Total deposits		105,000
Goodwill		$ 1,839					$ 1,839
Niagara Bancorporation
Business Acquisition [Line Items]
Number of banking offices | item	4
Assets	$ 67,000
Net cash used in Eagle acquisition and reimbursement of contract termination fee	7,325
Net assets acquired:
Total Loans, net of purchase accounting marks	33,000
Deposit based intangible	300
Total deposits	59,000
Goodwill	$ 50
FFNM | Minimum
Business Acquisition [Line Items]
Assets					$ 320,000