LOANS (Loans by credit quality indicator) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
2020	$ 2,473,911
2019	1,710,024
2018	1,255,022
2017	860,650
2016	488,559
2015 and Prior	1,265,027
Revolving	1,046,453
Total	9,099,646	$ 8,367,917
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	2,291,409
2019	1,606,716
2018	1,121,426
2017	745,690
2016	420,812
2015 and Prior	1,157,209
Revolving	966,547
Total	8,309,809	7,811,148
Nonpass
Financing Receivable, Credit Quality Indicator [Line Items]
Total		556,769
Watch
Financing Receivable, Credit Quality Indicator [Line Items]
2020	97,640
2019	76,279
2018	55,093
2017	60,241
2016	37,590
2015 and Prior	40,868
Revolving	50,169
Total	417,880
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	84,862
2019	27,029
2018	78,503
2017	54,719
2016	30,157
2015 and Prior	66,950
Revolving	29,737
Total	371,957
Paycheck Protection Program ("PPP") | Nonpass
Financing Receivable, Credit Quality Indicator [Line Items]
Total	64,900
Commercial and industrial | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
2020	400,283
2019	385,106
2018	220,302
2017	264,926
2016	135,630
2015 and Prior	365,568
Revolving	531,831
Total	2,303,646	2,530,809
Commercial and industrial | Commercial and industrial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	363,812
2019	355,625
2018	181,366
2017	229,869
2016	118,285
2015 and Prior	348,709
Revolving	480,474
Total	2,078,140	2,352,131
Commercial and industrial | Commercial and industrial | Nonpass
Financing Receivable, Credit Quality Indicator [Line Items]
Total		178,678
Commercial and industrial | Commercial and industrial | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
2020	32,475
2019	21,178
2018	17,393
2017	17,268
2016	6,597
2015 and Prior	2,381
Revolving	35,073
Total	132,365
Commercial and industrial | Commercial and industrial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	3,996
2019	8,303
2018	21,543
2017	17,789
2016	10,748
2015 and Prior	14,478
Revolving	16,284
Total	93,141
Commercial and industrial | Paycheck Protection Program ("PPP")
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,128,035
2019	0
2018	0
2017	0
2016	0
2015 and Prior	0
Revolving	0
Total	1,128,035	0
Commercial and industrial | Paycheck Protection Program ("PPP") | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,063,169
2019	0
2018	0
2017	0
2016	0
2015 and Prior	0
Revolving	0
Total	1,063,169
Commercial and industrial | Paycheck Protection Program ("PPP") | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
2020	34,691
2019	0
2018	0
2017	0
2016	0
2015 and Prior	0
Revolving	0
Total	34,691
Commercial and industrial | Paycheck Protection Program ("PPP") | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	30,175
2019	0
2018	0
2017	0
2016	0
2015 and Prior	0
Revolving	0
Total	30,175
Commercial and industrial | Owner occupied commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2020	243,730
2019	327,670
2018	312,072
2017	197,909
2016	127,412
2015 and Prior	251,315
Revolving	34,794
Total	1,494,902	1,472,704
Commercial and industrial | Owner occupied commercial real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	226,358
2019	313,472
2018	286,767
2017	165,497
2016	111,839
2015 and Prior	227,090
Revolving	32,287
Total	1,363,310	1,369,290
Commercial and industrial | Owner occupied commercial real estate | Nonpass
Financing Receivable, Credit Quality Indicator [Line Items]
Total		103,414
Commercial and industrial | Owner occupied commercial real estate | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
2020	8,449
2019	7,692
2018	10,430
2017	19,836
2016	6,255
2015 and Prior	9,276
Revolving	2,245
Total	64,183
Commercial and industrial | Owner occupied commercial real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	8,923
2019	6,506
2018	14,875
2017	12,576
2016	9,318
2015 and Prior	14,949
Revolving	262
Total	67,409
Commercial and industrial | Non-owner occupied commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2020	296,884
2019	425,696
2018	286,748
2017	229,706
2016	116,758
2015 and Prior	276,818
Revolving	27,073
Total	1,659,683	1,495,877
Commercial and industrial | Non-owner occupied commercial real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	256,678
2019	411,467
2018	252,071
2017	193,575
2016	105,474
2015 and Prior	253,755
Revolving	26,598
Total	1,499,618	1,429,760
Commercial and industrial | Non-owner occupied commercial real estate | Nonpass
Financing Receivable, Credit Quality Indicator [Line Items]
Total		66,117
Commercial and industrial | Non-owner occupied commercial real estate | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
2020	14,535
2019	9,949
2018	14,788
2017	20,394
2016	7,648
2015 and Prior	18,171
Revolving	475
Total	85,960
Commercial and industrial | Non-owner occupied commercial real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	25,671
2019	4,280
2018	19,889
2017	15,737
2016	3,636
2015 and Prior	4,892
Revolving	0
Total	74,105
Commercial and industrial | Real estate construction
Financing Receivable, Credit Quality Indicator [Line Items]
2020	191,289
2019	377,693
2018	241,670
2017	35,607
2016	29,747
2015 and Prior	24,406
Revolving	17,353
Total	917,765	1,027,081
Commercial and industrial | Real estate construction | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	188,216
2019	351,522
2018	235,386
2017	34,641
2016	14,609
2015 and Prior	23,189
Revolving	16,716
Total	864,279	984,736
Commercial and industrial | Real estate construction | Nonpass
Financing Receivable, Credit Quality Indicator [Line Items]
Total		42,345
Commercial and industrial | Real estate construction | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
2020	2,874
2019	24,153
2018	5,931
2017	280
2016	14,744
2015 and Prior	791
Revolving	637
Total	49,410
Commercial and industrial | Real estate construction | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	199
2019	2,018
2018	353
2017	686
2016	394
2015 and Prior	426
Revolving	0
Total	4,076
Agricultural and agricultural real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2020	105,844
2019	90,585
2018	69,180
2017	36,958
2016	20,928
2015 and Prior	49,735
Revolving	134,828
Total	508,058	565,837
Agricultural and agricultural real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	86,754
2019	76,196
2018	45,596
2017	29,713
2016	15,357
2015 and Prior	33,322
Revolving	114,403
Total	401,341	454,272
Agricultural and agricultural real estate | Nonpass
Financing Receivable, Credit Quality Indicator [Line Items]
Total		111,565
Agricultural and agricultural real estate | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
2020	4,527
2019	9,475
2018	5,127
2017	826
2016	1,772
2015 and Prior	3,651
Revolving	9,175
Total	34,553
Agricultural and agricultural real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	14,563
2019	4,914
2018	18,457
2017	6,419
2016	3,799
2015 and Prior	12,762
Revolving	11,250
Total	72,164
Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2020	82,487
2019	75,972
2018	103,766
2017	80,656
2016	53,131
2015 and Prior	274,071
Revolving	31,816
Total	701,899	832,277
Residential real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	81,558
2019	72,198
2018	101,789
2017	78,394
2016	51,293
2015 and Prior	250,936
Revolving	30,370
Total	666,538	790,226
Residential real estate | Nonpass
Financing Receivable, Credit Quality Indicator [Line Items]
Total		42,051
Residential real estate | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
2020	81
2019	3,462
2018	825
2017	1,402
2016	338
2015 and Prior	5,844
Revolving	346
Total	12,298
Residential real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	848
2019	312
2018	1,152
2017	860
2016	1,500
2015 and Prior	17,291
Revolving	1,100
Total	23,063
Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
2020	25,359
2019	27,302
2018	21,284
2017	14,888
2016	4,953
2015 and Prior	23,114
Revolving	268,758
Total	385,658	443,332
Consumer | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	24,864
2019	26,236
2018	18,451
2017	14,001
2016	3,955
2015 and Prior	20,208
Revolving	265,699
Total	373,414	430,733
Consumer | Nonpass
Financing Receivable, Credit Quality Indicator [Line Items]
Total		$ 12,599
Consumer | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
2020	8
2019	370
2018	599
2017	235
2016	236
2015 and Prior	754
Revolving	2,218
Total	4,420
Consumer | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	487
2019	696
2018	2,234
2017	652
2016	762
2015 and Prior	2,152
Revolving	841
Total	$ 7,824