LOANS (Impaired loans) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Receivables [Abstract]
Threshold period past due, nonperforming status of loans and leases	90 days
Unpaid Principal Balance
Total impaired loans with a related allowance	$ 19,333	$ 17,005
Total impaired loans without a related allowance	72,804	69,265
Total impaired loans held to maturity	92,137	86,270
Loan Balance
Total impaired loans with a related allowance	19,320	16,995
Total impaired loans without a related allowance	68,248	64,801
Total impaired loans held to maturity	87,568	81,796
Related Allowance Recorded	8,559	7,554
Avg. Loan Balance
Total impaired loans with a related allowance	17,759	15,399
Total impaired loans without a related allowance	63,062	66,900
Total impaired loans held to maturity	80,821	82,299
Interest Income Recognized
Total impaired loans with a related allowance	20	101
Total impaired loans without a related allowance	501	958
Total impaired loans held to maturity	521	1,059
Commercial
Unpaid Principal Balance
Total impaired loans with a related allowance	13,528	13,267
Total impaired loans without a related allowance	31,276	27,194
Total impaired loans held to maturity	44,804	40,461
Loan Balance
Total impaired loans with a related allowance	13,517	13,257
Total impaired loans without a related allowance	29,131	25,333
Total impaired loans held to maturity	42,648	38,590
Related Allowance Recorded	6,654	5,951
Avg. Loan Balance
Total impaired loans with a related allowance	13,247	9,162
Total impaired loans without a related allowance	25,936	23,052
Total impaired loans held to maturity	39,183	32,214
Interest Income Recognized
Total impaired loans with a related allowance	13	58
Total impaired loans without a related allowance	384	548
Total impaired loans held to maturity	397	606
Commercial | Commercial
Unpaid Principal Balance
Total impaired loans with a related allowance	12,107	12,376
Total impaired loans without a related allowance	14,467	13,616
Total impaired loans held to maturity	26,574	25,992
Loan Balance
Total impaired loans with a related allowance	12,096	12,366
Total impaired loans without a related allowance	12,402	11,836
Total impaired loans held to maturity	24,498	24,202
Related Allowance Recorded	6,301	5,733
Avg. Loan Balance
Total impaired loans with a related allowance	12,046	4,741
Total impaired loans without a related allowance	11,928	10,052
Total impaired loans held to maturity	23,974	14,793
Interest Income Recognized
Total impaired loans with a related allowance	7	33
Total impaired loans without a related allowance	330	299
Total impaired loans held to maturity	337	332
Commercial | Commercial real estate
Unpaid Principal Balance
Total impaired loans with a related allowance	1,421	891
Total impaired loans without a related allowance	16,809	13,578
Total impaired loans held to maturity	18,230	14,469
Loan Balance
Total impaired loans with a related allowance	1,421	891
Total impaired loans without a related allowance	16,729	13,497
Total impaired loans held to maturity	18,150	14,388
Related Allowance Recorded	353	218
Avg. Loan Balance
Total impaired loans with a related allowance	1,201	4,421
Total impaired loans without a related allowance	14,008	13,000
Total impaired loans held to maturity	15,209	17,421
Interest Income Recognized
Total impaired loans with a related allowance	6	25
Total impaired loans without a related allowance	54	249
Total impaired loans held to maturity	60	274
Agricultural and agricultural real estate
Unpaid Principal Balance
Total impaired loans with a related allowance	3,280	1,718
Total impaired loans without a related allowance	19,538	16,836
Total impaired loans held to maturity	22,818	18,554
Loan Balance
Total impaired loans with a related allowance	3,280	1,718
Total impaired loans without a related allowance	17,195	14,233
Total impaired loans held to maturity	20,475	15,951
Related Allowance Recorded	1,099	686
Avg. Loan Balance
Total impaired loans with a related allowance	2,225	2,165
Total impaired loans without a related allowance	14,373	14,781
Total impaired loans held to maturity	16,598	16,946
Interest Income Recognized
Total impaired loans with a related allowance	1	2
Total impaired loans without a related allowance	16	5
Total impaired loans held to maturity	17	7
Residential real estate
Unpaid Principal Balance
Total impaired loans with a related allowance	1,253	647
Total impaired loans without a related allowance	17,370	19,604
Total impaired loans held to maturity	18,623	20,251
Loan Balance
Total impaired loans with a related allowance	1,253	647
Total impaired loans without a related allowance	17,366	19,604
Total impaired loans held to maturity	18,619	20,251
Related Allowance Recorded	153	168
Avg. Loan Balance
Total impaired loans with a related allowance	1,012	1,138
Total impaired loans without a related allowance	17,933	23,950
Total impaired loans held to maturity	18,945	25,088
Interest Income Recognized
Total impaired loans with a related allowance	0	12
Total impaired loans without a related allowance	76	308
Total impaired loans held to maturity	76	320
Consumer
Unpaid Principal Balance
Total impaired loans with a related allowance	1,272	1,373
Total impaired loans without a related allowance	4,620	5,631
Total impaired loans held to maturity	5,892	7,004
Loan Balance
Total impaired loans with a related allowance	1,270	1,373
Total impaired loans without a related allowance	4,556	5,631
Total impaired loans held to maturity	5,826	7,004
Related Allowance Recorded	653	749
Avg. Loan Balance
Total impaired loans with a related allowance	1,275	2,934
Total impaired loans without a related allowance	4,820	5,117
Total impaired loans held to maturity	6,095	8,051
Interest Income Recognized
Total impaired loans with a related allowance	6	29
Total impaired loans without a related allowance	25	97
Total impaired loans held to maturity	$ 31	$ 126