LOANS (Impaired loans) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Dec. 31, 2018
Receivables [Abstract]
Threshold period past due, nonperforming status of loans and leases		90 days
Unpaid Principal Balance
Impaired loans with a related allowance	$ 17,876	$ 17,876	$ 17,005
Impaired loans without a related allowance	73,689	73,689	69,265
Total impaired loans held to maturity	91,565	91,565	86,270
Loan Balance
Impaired loans with a related allowance	17,864	17,864	16,995
Impaired loans without a related allowance	68,129	68,129	64,801
Total impaired loans held to maturity	85,993	85,993	81,796
Related Allowance Recorded	8,114	8,114	7,554
Avg. Loan Balance
Impaired loans with a related allowance	18,297	18,251	15,399
Impaired loans without a related allowance	69,893	67,805	66,900
Total impaired loans held to maturity	88,190	86,056	82,299
Interest Income Recognized
Impaired loans with a related allowance	27	54	101
Impaired loans without a related allowance	358	1,153	958
Total impaired loans held to maturity	385	1,207	1,059
Commercial
Unpaid Principal Balance
Impaired loans with a related allowance	12,776	12,776	13,267
Impaired loans without a related allowance	32,995	32,995	27,194
Total impaired loans held to maturity	45,771	45,771	40,461
Loan Balance
Impaired loans with a related allowance	12,766	12,766	13,257
Impaired loans without a related allowance	30,502	30,502	25,333
Total impaired loans held to maturity	43,268	43,268	38,590
Related Allowance Recorded	6,432	6,432	5,951
Avg. Loan Balance
Impaired loans with a related allowance	12,995	13,016	9,162
Impaired loans without a related allowance	32,426	29,886	23,052
Total impaired loans held to maturity	45,421	42,902	32,214
Interest Income Recognized
Impaired loans with a related allowance	6	26	58
Impaired loans without a related allowance	274	842	548
Total impaired loans held to maturity	280	868	606
Commercial | Commercial
Unpaid Principal Balance
Impaired loans with a related allowance	11,025	11,025	12,376
Impaired loans without a related allowance	14,752	14,752	13,616
Total impaired loans held to maturity	25,777	25,777	25,992
Loan Balance
Impaired loans with a related allowance	11,015	11,015	12,366
Impaired loans without a related allowance	12,340	12,340	11,836
Total impaired loans held to maturity	23,355	23,355	24,202
Related Allowance Recorded	6,124	6,124	5,733
Avg. Loan Balance
Impaired loans with a related allowance	11,399	11,630	4,741
Impaired loans without a related allowance	13,529	12,989	10,052
Total impaired loans held to maturity	24,928	24,619	14,793
Interest Income Recognized
Impaired loans with a related allowance	0	9	33
Impaired loans without a related allowance	186	627	299
Total impaired loans held to maturity	186	636	332
Commercial | Commercial real estate
Unpaid Principal Balance
Impaired loans with a related allowance	1,751	1,751	891
Impaired loans without a related allowance	18,243	18,243	13,578
Total impaired loans held to maturity	19,994	19,994	14,469
Loan Balance
Impaired loans with a related allowance	1,751	1,751	891
Impaired loans without a related allowance	18,162	18,162	13,497
Total impaired loans held to maturity	19,913	19,913	14,388
Related Allowance Recorded	308	308	218
Avg. Loan Balance
Impaired loans with a related allowance	1,596	1,386	4,421
Impaired loans without a related allowance	18,897	16,897	13,000
Total impaired loans held to maturity	20,493	18,283	17,421
Interest Income Recognized
Impaired loans with a related allowance	6	17	25
Impaired loans without a related allowance	88	215	249
Total impaired loans held to maturity	94	232	274
Agricultural and agricultural real estate
Unpaid Principal Balance
Impaired loans with a related allowance	2,979	2,979	1,718
Impaired loans without a related allowance	20,137	20,137	16,836
Total impaired loans held to maturity	23,116	23,116	18,554
Loan Balance
Impaired loans with a related allowance	2,979	2,979	1,718
Impaired loans without a related allowance	17,094	17,094	14,233
Total impaired loans held to maturity	20,073	20,073	15,951
Related Allowance Recorded	1,084	1,084	686
Avg. Loan Balance
Impaired loans with a related allowance	3,100	2,881	2,165
Impaired loans without a related allowance	16,958	16,243	14,781
Total impaired loans held to maturity	20,058	19,124	16,946
Interest Income Recognized
Impaired loans with a related allowance	17	17	2
Impaired loans without a related allowance	12	45	5
Total impaired loans held to maturity	29	62	7
Residential real estate
Unpaid Principal Balance
Impaired loans with a related allowance	999	999	647
Impaired loans without a related allowance	16,578	16,578	19,604
Total impaired loans held to maturity	17,577	17,577	20,251
Loan Balance
Impaired loans with a related allowance	999	999	647
Impaired loans without a related allowance	16,553	16,553	19,604
Total impaired loans held to maturity	17,552	17,552	20,251
Related Allowance Recorded	123	123	168
Avg. Loan Balance
Impaired loans with a related allowance	1,086	1,157	1,138
Impaired loans without a related allowance	16,612	17,362	23,950
Total impaired loans held to maturity	17,698	18,519	25,088
Interest Income Recognized
Impaired loans with a related allowance	3	3	12
Impaired loans without a related allowance	69	220	308
Total impaired loans held to maturity	72	223	320
Consumer
Unpaid Principal Balance
Impaired loans with a related allowance	1,122	1,122	1,373
Impaired loans without a related allowance	3,979	3,979	5,631
Total impaired loans held to maturity	5,101	5,101	7,004
Loan Balance
Impaired loans with a related allowance	1,120	1,120	1,373
Impaired loans without a related allowance	3,980	3,980	5,631
Total impaired loans held to maturity	5,100	5,100	7,004
Related Allowance Recorded	475	475	749
Avg. Loan Balance
Impaired loans with a related allowance	1,116	1,197	2,934
Impaired loans without a related allowance	3,897	4,314	5,117
Total impaired loans held to maturity	5,013	5,511	8,051
Interest Income Recognized
Impaired loans with a related allowance	1	8	29
Impaired loans without a related allowance	3	46	97
Total impaired loans held to maturity	$ 4	$ 54	$ 126