LOANS (Troubled debt restructuring) (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($) loan	Jun. 30, 2019 USD ($) loan numberOfBankLocations	Jun. 30, 2020 USD ($) loan	Jun. 30, 2019 USD ($) loan	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	1	3	2	4
Pre- Modification Recorded Investment	$ 60	$ 240	$ 92	$ 276
Post- Modification Recorded Investment	$ 66	$ 246	$ 98	$ 288
With Payment Defaults
Number of Loans | loan	0	1	1	3
Recorded Investment	$ 0	$ 61	$ 238	$ 253
Total Past Due	22,132		22,132			$ 31,928
Current	9,133,089		9,133,089			8,259,441
Nonaccrual	91,609		91,609			76,548
Loans receivable	9,246,830		9,246,830			8,367,917
Allowance for credit loss	119,937	63,850	119,937	63,850	$ 97,350	70,395	$ 62,639	$ 61,963
Charge-offs	(3,564)	(4,780)	(9,865)	(6,730)
Recoveries	1,144	1,073	2,464	2,064
Provision for Loan and Lease Losses	25,007	$ 4,918	48,316	6,553
Provision			44,872	$ 6,553
Impact of ASU 2016-13 adoption
With Payment Defaults
Allowance for credit loss						12,071
30-59 Days Past Due
With Payment Defaults
Total Past Due	17,037		17,037			25,322
60-89 Days Past Due
With Payment Defaults
Total Past Due	3,735		3,735			2,501
90 Days or More Past Due
With Payment Defaults
Total Past Due	$ 1,360		$ 1,360			4,105
Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	0	0
Pre- Modification Recorded Investment		$ 0
Post- Modification Recorded Investment	$ 0	$ 0
Commercial and industrial | Commercial and industrial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	0	0	0	0
Pre- Modification Recorded Investment	$ 0	$ 0	$ 0	$ 0
Post- Modification Recorded Investment	$ 0	$ 0	$ 0	$ 0
With Payment Defaults
Number of Loans | loan	0	0	0	0
Recorded Investment	$ 0	$ 0	$ 0	$ 0
Total Past Due	4,815		4,815			9,924
Current	2,338,143		2,338,143			2,491,110
Nonaccrual	21,442		21,442			29,775
Loans receivable	2,364,400		2,364,400			2,530,809
Allowance for credit loss	32,531	27,680	32,531	27,680	32,463	30,787	27,250	26,306
Charge-offs	(2,767)	(3,971)	(8,363)	(4,951)
Recoveries	432	276	784	584
Provision for Loan and Lease Losses	2,403	$ 4,125
Provision			6,176	$ 5,741
Commercial and industrial | Commercial and industrial | Impact of ASU 2016-13 adoption
With Payment Defaults
Allowance for credit loss						3,147
Commercial and industrial | Commercial and industrial | 30-59 Days Past Due
With Payment Defaults
Total Past Due	4,587		4,587			5,121
Commercial and industrial | Commercial and industrial | 60-89 Days Past Due
With Payment Defaults
Total Past Due	228		228			904
Commercial and industrial | Commercial and industrial | 90 Days or More Past Due
With Payment Defaults
Total Past Due	$ 0		$ 0			3,899
Commercial and industrial | Paycheck Protection Program ("PPP")
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	0	0	0	0
Pre- Modification Recorded Investment	$ 0	$ 0	$ 0	$ 0
Post- Modification Recorded Investment	$ 0	$ 0	$ 0	$ 0
With Payment Defaults
Number of Loans | loan	0	0	0	0
Recorded Investment	$ 0	$ 0	$ 0	$ 0
Total Past Due	0		0
Current	1,124,430		1,124,430
Nonaccrual	0		0
Loans receivable	1,124,430		1,124,430			0
Allowance for credit loss	0		0		0	0
Charge-offs	0		0
Recoveries	0		0
Provision for Loan and Lease Losses	0
Provision			0
Commercial and industrial | Paycheck Protection Program ("PPP") | Impact of ASU 2016-13 adoption
With Payment Defaults
Allowance for credit loss						0
Commercial and industrial | Paycheck Protection Program ("PPP") | 30-59 Days Past Due
With Payment Defaults
Total Past Due	0		0
Commercial and industrial | Paycheck Protection Program ("PPP") | 60-89 Days Past Due
With Payment Defaults
Total Past Due	0		0
Commercial and industrial | Paycheck Protection Program ("PPP") | 90 Days or More Past Due
With Payment Defaults
Total Past Due	0		$ 0
Commercial and industrial | Owner occupied commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan			0	0
Pre- Modification Recorded Investment			$ 0	$ 0
Post- Modification Recorded Investment			$ 0	$ 0
With Payment Defaults
Number of Loans | loan			0	0
Recorded Investment			$ 0	$ 0
Total Past Due	1,249		1,249			4,177
Current	1,406,437		1,406,437			1,461,589
Nonaccrual	25,585		25,585			6,938
Loans receivable	1,433,271		1,433,271			1,472,704
Allowance for credit loss	23,402	6,182	23,402	6,182	10,336	8,214	6,330	6,525
Charge-offs	(213)	(13)	(213)	(36)
Recoveries	191	4	192	93
Provision for Loan and Lease Losses	13,088	(139)
Provision			15,616	$ (400)
Commercial and industrial | Owner occupied commercial real estate | Impact of ASU 2016-13 adoption
With Payment Defaults
Allowance for credit loss						(407)
Commercial and industrial | Owner occupied commercial real estate | 30-59 Days Past Due
With Payment Defaults
Total Past Due	90		90			3,487
Commercial and industrial | Owner occupied commercial real estate | 60-89 Days Past Due
With Payment Defaults
Total Past Due	1,159		1,159			690
Commercial and industrial | Owner occupied commercial real estate | 90 Days or More Past Due
With Payment Defaults
Total Past Due	0		$ 0			0
Commercial and industrial | Non-owner occupied commercial real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan			0	0
Pre- Modification Recorded Investment			$ 0	$ 0
Post- Modification Recorded Investment			$ 0	$ 0
With Payment Defaults
Number of Loans | loan			0	0
Recorded Investment			$ 0	$ 0
Total Past Due	2,934		2,934			695
Current	1,536,928		1,536,928			1,493,619
Nonaccrual	3,761		3,761			1,563
Loans receivable	1,543,623		1,543,623			1,495,877
Allowance for credit loss	10,162	7,482	10,162	7,482	8,321	7,802	7,126	7,430
Charge-offs	(19)	0	(19)	0
Recoveries	8	60	8	100
Provision for Loan and Lease Losses	1,852	$ 296
Provision			5,205	$ (48)
Commercial and industrial | Non-owner occupied commercial real estate | Impact of ASU 2016-13 adoption
With Payment Defaults
Allowance for credit loss						(2,834)
Commercial and industrial | Non-owner occupied commercial real estate | 30-59 Days Past Due
With Payment Defaults
Total Past Due	2,776		2,776			614
Commercial and industrial | Non-owner occupied commercial real estate | 60-89 Days Past Due
With Payment Defaults
Total Past Due	158		158			81
Commercial and industrial | Non-owner occupied commercial real estate | 90 Days or More Past Due
With Payment Defaults
Total Past Due	$ 0		$ 0			0
Commercial and industrial | Real estate construction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	0	0	0	0
Pre- Modification Recorded Investment	$ 0	$ 0	$ 0	$ 0
Post- Modification Recorded Investment	$ 0	$ 0	$ 0	$ 0
With Payment Defaults
Number of Loans | loan	0	0	0	0
Recorded Investment	$ 0	$ 0	$ 0	$ 0
Total Past Due	2,298		2,298			5,761
Current	1,112,172		1,112,172			1,020,153
Nonaccrual	1,373		1,373			1,167
Loans receivable	1,115,843		1,115,843			1,027,081
Allowance for credit loss	28,667	10,010	28,667	10,010	22,951	11,599	9,994	9,679
Charge-offs	(84)	(101)	(105)	(155)
Recoveries	210	124	215	128
Provision for Loan and Lease Losses	5,590	$ (7)
Provision			13,545	$ 358
Commercial and industrial | Real estate construction | Impact of ASU 2016-13 adoption
With Payment Defaults
Allowance for credit loss						3,413
Commercial and industrial | Real estate construction | 30-59 Days Past Due
With Payment Defaults
Total Past Due	2,298		2,298			5,689
Commercial and industrial | Real estate construction | 60-89 Days Past Due
With Payment Defaults
Total Past Due	0		0			72
Commercial and industrial | Real estate construction | 90 Days or More Past Due
With Payment Defaults
Total Past Due	$ 0		$ 0			0
Agricultural and agricultural real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	0	0	0	0
Pre- Modification Recorded Investment	$ 0	$ 0	$ 0	$ 0
Post- Modification Recorded Investment	$ 0	$ 0	$ 0	$ 0
With Payment Defaults
Number of Loans | loan	0	0	0	0
Recorded Investment	$ 0	$ 0	$ 0	$ 0
Total Past Due	4,892		4,892			3,839
Current	496,541		496,541			541,455
Nonaccrual	19,340		19,340			20,543
Loans receivable	520,773		520,773			565,837
Allowance for credit loss	5,701	5,986	5,701	5,986	4,797	5,673	5,518	4,914
Charge-offs	(1)	(48)	(254)	(427)
Recoveries	0	1	826	329
Provision for Loan and Lease Losses	905	$ 515
Provision			(164)	$ 1,170
Agricultural and agricultural real estate | Impact of ASU 2016-13 adoption
With Payment Defaults
Allowance for credit loss						(380)
Agricultural and agricultural real estate | 30-59 Days Past Due
With Payment Defaults
Total Past Due	4,209		4,209			3,734
Agricultural and agricultural real estate | 60-89 Days Past Due
With Payment Defaults
Total Past Due	600		600			79
Agricultural and agricultural real estate | 90 Days or More Past Due
With Payment Defaults
Total Past Due	$ 83		$ 83			26
Residential real estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	1	3	2	4
Pre- Modification Recorded Investment	$ 60	$ 240	$ 92	$ 276
Post- Modification Recorded Investment	$ 66	$ 246	$ 98	$ 288
With Payment Defaults
Number of Loans | loan	0	1	1	3
Recorded Investment	$ 0	$ 61	$ 238	$ 253
Total Past Due	2,932		2,932			4,370
Current	717,246		717,246			814,840
Nonaccrual	15,584		15,584			13,067
Loans receivable	735,762		735,762			832,277
Allowance for credit loss	9,304	1,592	9,304	1,592	8,725	1,504	1,623	1,813
Charge-offs	(235)	(201)	(314)	(341)
Recoveries	92	34	95	86
Provision for Loan and Lease Losses	722	$ 136
Provision			3,202	$ 34
Residential real estate | Impact of ASU 2016-13 adoption
With Payment Defaults
Allowance for credit loss						4,817
Residential real estate | 30-59 Days Past Due
With Payment Defaults
Total Past Due	483		483			4,166
Residential real estate | 60-89 Days Past Due
With Payment Defaults
Total Past Due	1,242		1,242			24
Residential real estate | 90 Days or More Past Due
With Payment Defaults
Total Past Due	1,207		$ 1,207			180
Residential real estate | Real estate construction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | numberOfBankLocations		0
Pre- Modification Recorded Investment		$ 0
Post- Modification Recorded Investment	$ 0	$ 0
Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	0	0	0	0
Pre- Modification Recorded Investment	$ 0	$ 0	$ 0	$ 0
Post- Modification Recorded Investment	$ 0	$ 0	$ 0	$ 0
With Payment Defaults
Number of Loans | loan	0	0	0	0
Recorded Investment	$ 0	$ 0	$ 0	$ 0
Total Past Due	3,012		3,012			3,162
Current	401,192		401,192			436,675
Nonaccrual	4,524		4,524			3,495
Loans receivable	408,728		408,728			443,332
Allowance for credit loss	10,170	4,918	10,170	4,918	$ 9,757	4,816	$ 4,798	$ 5,296
Charge-offs	(245)	(446)	(597)	(820)
Recoveries	211	574	344	744
Provision for Loan and Lease Losses	447	$ (8)
Provision			1,292	$ (302)
Consumer | Impact of ASU 2016-13 adoption
With Payment Defaults
Allowance for credit loss						4,315
Consumer | 30-59 Days Past Due
With Payment Defaults
Total Past Due	2,594		2,594			2,511
Consumer | 60-89 Days Past Due
With Payment Defaults
Total Past Due	348		348			651
Consumer | 90 Days or More Past Due
With Payment Defaults
Total Past Due	$ 70		$ 70			$ 0