GOODWILL AND OTHER INTANGIBLE ASSETS (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	May 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Aug. 31, 2016	Apr. 30, 2016	Dec. 31, 2014
Goodwill	$ 20,389		$ 5,694
Deposit based intangible assets	4,504		$ 1,922
Amortization expense	148
Amortization expense year one	523
Amortization expense year two	523
Amortization expense year three	523
Amortization expense year four	523
Amortization expense year five	$ 523
PFC
Goodwill							$ 3,805
Deposit based intangible assets							$ 1,206
Eagle River
Goodwill				$ 1,839		$ 1,839
Deposit based intangible assets				$ 993
Niagara Bancorporation
Goodwill					$ 50
Deposit based intangible assets					$ 300
FFNM
Goodwill		$ 14,695
Deposit based intangible assets		$ 2,729