LOANS (Allowance for credit losses on financing receivables) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Credit Losses	$ 8,447		$ 8,171
Collectively Evaluated for Credit Losses	94,930		62,224
Total	103,377	$ 119,937	70,395	$ 66,222	$ 63,850	$ 61,963
Loans Individually Evaluated for Credit Losses	59,916		87,052
Loans Collectively Evaluated for Credit Losses	9,039,730		8,280,865
Total	9,099,646		8,367,917
Commercial and industrial | Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Credit Losses	5,745		6,276
Collectively Evaluated for Credit Losses	28,853		24,511
Total	34,598	32,531	30,787	28,424	27,680	26,306
Loans Individually Evaluated for Credit Losses	19,420		31,814
Loans Collectively Evaluated for Credit Losses	2,284,226		2,498,995
Total	2,303,646		2,530,809
Commercial and industrial | Paycheck Protection Program ("PPP")
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Credit Losses	0
Collectively Evaluated for Credit Losses	0
Total	0	0	0
Loans Individually Evaluated for Credit Losses	0
Loans Collectively Evaluated for Credit Losses	1,128,035
Total	1,128,035		0
Commercial and industrial | Owner occupied commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Credit Losses	263		351
Collectively Evaluated for Credit Losses	10,966		7,863
Total	11,229	23,402	8,214	7,250	6,182	6,525
Loans Individually Evaluated for Credit Losses	11,833		9,468
Loans Collectively Evaluated for Credit Losses	1,483,069		1,463,236
Total	1,494,902		1,472,704
Commercial and industrial | Non-owner occupied commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Credit Losses	0		33
Collectively Evaluated for Credit Losses	12,127		7,769
Total	12,127	10,162	7,802	7,747	7,482	7,430
Loans Individually Evaluated for Credit Losses	3,644		1,730
Loans Collectively Evaluated for Credit Losses	1,656,039		1,494,147
Total	1,659,683		1,495,877
Commercial and industrial | Real estate construction
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Credit Losses	74		0
Collectively Evaluated for Credit Losses	20,713		11,599
Total	20,787	28,667	11,599	10,688	10,010	9,679
Loans Individually Evaluated for Credit Losses	1,284		685
Loans Collectively Evaluated for Credit Losses	916,481		1,026,396
Total	917,765		1,027,081
Agricultural and agricultural real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Credit Losses	1,847		916
Collectively Evaluated for Credit Losses	3,494		4,757
Total	5,341	5,701	5,673	5,370	5,986	4,914
Loans Individually Evaluated for Credit Losses	17,906		18,554
Loans Collectively Evaluated for Credit Losses	490,152		547,283
Total	508,058		565,837
Residential real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Credit Losses	135		176
Collectively Evaluated for Credit Losses	9,536		1,328
Total	9,671	9,304	1,504	1,805	1,592	1,813
Loans Individually Evaluated for Credit Losses	4,661		20,678
Loans Collectively Evaluated for Credit Losses	697,238		811,599
Total	701,899		832,277
Consumer
Financing Receivable, Allowance for Credit Loss [Line Items]
Individually Evaluated for Credit Losses	383		419
Collectively Evaluated for Credit Losses	9,241		4,397
Total	9,624	$ 10,170	4,816	$ 4,938	$ 4,918	$ 5,296
Loans Individually Evaluated for Credit Losses	1,168		4,123
Loans Collectively Evaluated for Credit Losses	384,490		439,209
Total	$ 385,658		$ 443,332