GOODWILL, CORE DEPOSIT PREMIUM AND OTHER INTANGIBLE ASSETS (Book value, fair value of commercial serving rights and impairment) (Details) - USD ($)	6 Months Ended	9 Months Ended	12 Months Ended
	Jun. 30, 2020	Sep. 30, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Valuation Allowance		$ 2,100,000
15 Years
Finite-Lived Intangible Assets [Line Items]
Book Value		1,618,000	$ 1,482,000
Fair Value		1,084,000	1,368,000
Valuation Allowance	$ 114,000	534,000
30 Years
Finite-Lived Intangible Assets [Line Items]
Book Value		5,850,000	5,050,000
Fair Value		3,739,000	4,253,000
Valuation Allowance	797,000	2,111,000
Less Than 20 Years
Finite-Lived Intangible Assets [Line Items]
Book Value		118,000	129,000
Fair Value		294,000	285,000
Valuation Allowance	0	0	0
More Than 20 Years
Finite-Lived Intangible Assets [Line Items]
Book Value		811,000	986,000
Fair Value		1,203,000	1,309,000
Valuation Allowance	0	0	0
First Bank & Trust | 15 Years
Finite-Lived Intangible Assets [Line Items]
Book Value		1,618,000	1,482,000
Fair Value		1,084,000	1,368,000
Valuation Allowance	114,000	534,000
First Bank & Trust | 30 Years
Finite-Lived Intangible Assets [Line Items]
Book Value		5,850,000	5,050,000
Fair Value		3,739,000	4,253,000
Valuation Allowance	797,000	2,111,000
Premier Valley Bank | Less Than 20 Years
Finite-Lived Intangible Assets [Line Items]
Book Value		1,000	1,000
Fair Value		9,000	13,000
Valuation Allowance	0	0
Premier Valley Bank | More Than 20 Years
Finite-Lived Intangible Assets [Line Items]
Book Value		94,000	135,000
Fair Value		156,000	161,000
Valuation Allowance	0	0
Wisconsin Bank & Trust | Less Than 20 Years
Finite-Lived Intangible Assets [Line Items]
Book Value		117,000	128,000
Fair Value		285,000	272,000
Valuation Allowance	0	0
Wisconsin Bank & Trust | More Than 20 Years
Finite-Lived Intangible Assets [Line Items]
Book Value		717,000	851,000
Fair Value		1,047,000	$ 1,148,000
Valuation Allowance	$ 0	$ 0