LOANS (Loans by Credit Quality Indicator) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Recorded Investment [Line Items]
2020	$ 3,119,680
2019	1,842,640
2018	1,287,023
2017	842,221
2016	485,454
2015 and Prior	1,254,784
Revolving	1,191,249
Total	10,023,051	$ 8,367,917
Pass
Financing Receivable, Recorded Investment [Line Items]
2020	2,847,203
2019	1,649,219
2018	1,131,756
2017	727,712
2016	408,380
2015 and Prior	1,091,908
Revolving	1,084,202
Total	8,940,380	7,811,148
Nonpass
Financing Receivable, Recorded Investment [Line Items]
Total		556,769
Watch
Financing Receivable, Recorded Investment [Line Items]
2020	129,037
2019	141,385
2018	80,970
2017	58,813
2016	44,512
2015 and Prior	76,144
Revolving	74,056
Total	604,917
Substandard
Financing Receivable, Recorded Investment [Line Items]
2020	143,440
2019	52,036
2018	74,297
2017	55,696
2016	32,562
2015 and Prior	86,732
Revolving	32,991
Total	477,754
Paycheck Protection Program ("PPP") | Nonpass
Financing Receivable, Recorded Investment [Line Items]
Total	77,100
Commercial and industrial | Commercial and industrial
Financing Receivable, Recorded Investment [Line Items]
2020	622,451
2019	381,759
2018	197,442
2017	245,675
2016	118,180
2015 and Prior	359,845
Revolving	609,447
Total	2,534,799	2,530,809
Commercial and industrial | Commercial and industrial | Pass
Financing Receivable, Recorded Investment [Line Items]
2020	557,853
2019	340,809
2018	168,873
2017	215,696
2016	101,010
2015 and Prior	337,834
Revolving	541,627
Total	2,263,702	2,352,131
Commercial and industrial | Commercial and industrial | Nonpass
Financing Receivable, Recorded Investment [Line Items]
Total		178,678
Commercial and industrial | Commercial and industrial | Watch
Financing Receivable, Recorded Investment [Line Items]
2020	41,574
2019	24,676
2018	19,672
2017	14,262
2016	8,072
2015 and Prior	2,474
Revolving	49,432
Total	160,162
Commercial and industrial | Commercial and industrial | Substandard
Financing Receivable, Recorded Investment [Line Items]
2020	23,024
2019	16,274
2018	8,897
2017	15,717
2016	9,098
2015 and Prior	19,537
Revolving	18,388
Total	110,935
Commercial and industrial | Paycheck Protection Program ("PPP")
Financing Receivable, Recorded Investment [Line Items]
2020	957,785
2019	0
2018	0
2017	0
2016	0
2015 and Prior	0
Revolving	0
Total	957,785	0
Commercial and industrial | Paycheck Protection Program ("PPP") | Pass
Financing Receivable, Recorded Investment [Line Items]
2020	880,709
2019	0
2018	0
2017	0
2016	0
2015 and Prior	0
Revolving	0
Total	880,709
Commercial and industrial | Paycheck Protection Program ("PPP") | Watch
Financing Receivable, Recorded Investment [Line Items]
2020	22,533
2019	0
2018	0
2017	0
2016	0
2015 and Prior	0
Revolving	0
Total	22,533
Commercial and industrial | Paycheck Protection Program ("PPP") | Substandard
Financing Receivable, Recorded Investment [Line Items]
2020	54,543
2019	0
2018	0
2017	0
2016	0
2015 and Prior	0
Revolving	0
Total	54,543
Commercial and industrial | Owner occupied commercial real estate
Financing Receivable, Recorded Investment [Line Items]
2020	431,921
2019	392,687
2018	334,894
2017	202,428
2016	124,531
2015 and Prior	250,770
Revolving	39,175
Total	1,776,406	1,472,704
Commercial and industrial | Owner occupied commercial real estate | Pass
Financing Receivable, Recorded Investment [Line Items]
2020	400,662
2019	369,401
2018	300,242
2017	167,470
2016	107,234
2015 and Prior	213,780
Revolving	33,759
Total	1,592,548	1,369,290
Commercial and industrial | Owner occupied commercial real estate | Nonpass
Financing Receivable, Recorded Investment [Line Items]
Total		103,414
Commercial and industrial | Owner occupied commercial real estate | Watch
Financing Receivable, Recorded Investment [Line Items]
2020	15,345
2019	13,764
2018	22,488
2017	20,811
2016	8,717
2015 and Prior	15,282
Revolving	4,311
Total	100,718
Commercial and industrial | Owner occupied commercial real estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
2020	15,914
2019	9,522
2018	12,164
2017	14,147
2016	8,580
2015 and Prior	21,708
Revolving	1,105
Total	83,140
Commercial and industrial | Non-owner occupied commercial real estate
Financing Receivable, Recorded Investment [Line Items]
2020	388,447
2019	481,561
2018	353,464
2017	229,871
2016	138,171
2015 and Prior	299,885
Revolving	30,082
Total	1,921,481	1,495,877
Commercial and industrial | Non-owner occupied commercial real estate | Pass
Financing Receivable, Recorded Investment [Line Items]
2020	334,722
2019	411,301
2018	305,456
2017	194,101
2016	108,070
2015 and Prior	233,153
Revolving	24,466
Total	1,611,269	1,429,760
Commercial and industrial | Non-owner occupied commercial real estate | Nonpass
Financing Receivable, Recorded Investment [Line Items]
Total		66,117
Commercial and industrial | Non-owner occupied commercial real estate | Watch
Financing Receivable, Recorded Investment [Line Items]
2020	22,826
2019	55,225
2018	24,718
2017	18,724
2016	20,954
2015 and Prior	45,672
Revolving	5,114
Total	193,233
Commercial and industrial | Non-owner occupied commercial real estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
2020	30,899
2019	15,035
2018	23,290
2017	17,046
2016	9,147
2015 and Prior	21,060
Revolving	502
Total	116,979
Commercial and industrial | Real estate construction
Financing Receivable, Recorded Investment [Line Items]
2020	313,926
2019	339,097
2018	161,610
2017	12,957
2016	7,048
2015 and Prior	5,856
Revolving	22,726
Total	863,220	1,027,081
Commercial and industrial | Real estate construction | Pass
Financing Receivable, Recorded Investment [Line Items]
2020	311,625
2019	309,678
2018	157,171
2017	12,625
2016	6,954
2015 and Prior	5,110
Revolving	21,431
Total	824,594	984,736
Commercial and industrial | Real estate construction | Nonpass
Financing Receivable, Recorded Investment [Line Items]
Total		42,345
Commercial and industrial | Real estate construction | Watch
Financing Receivable, Recorded Investment [Line Items]
2020	2,105
2019	26,659
2018	2,403
2017	332
2016	55
2015 and Prior	388
Revolving	1,295
Total	33,237
Commercial and industrial | Real estate construction | Substandard
Financing Receivable, Recorded Investment [Line Items]
2020	196
2019	2,760
2018	2,036
2017	0
2016	39
2015 and Prior	358
Revolving	0
Total	5,389
Agricultural and agricultural real estate
Financing Receivable, Recorded Investment [Line Items]
2020	209,481
2019	114,190
2018	94,722
2017	48,458
2016	25,058
2015 and Prior	50,805
Revolving	171,812
Total	714,526	565,837
Agricultural and agricultural real estate | Pass
Financing Receivable, Recorded Investment [Line Items]
2020	171,578
2019	90,944
2018	62,349
2017	39,252
2016	17,626
2015 and Prior	37,696
Revolving	148,456
Total	567,901	454,272
Agricultural and agricultural real estate | Nonpass
Financing Receivable, Recorded Investment [Line Items]
Total		111,565
Agricultural and agricultural real estate | Watch
Financing Receivable, Recorded Investment [Line Items]
2020	20,500
2019	16,202
2018	8,854
2017	2,448
2016	3,515
2015 and Prior	3,157
Revolving	12,282
Total	66,958
Agricultural and agricultural real estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
2020	17,403
2019	7,044
2018	23,519
2017	6,758
2016	3,917
2015 and Prior	9,952
Revolving	11,074
Total	79,667
Residential real estate
Financing Receivable, Recorded Investment [Line Items]
2020	157,983
2019	104,389
2018	123,549
2017	86,958
2016	67,478
2015 and Prior	265,518
Revolving	34,567
Total	840,442	832,277
Residential real estate | Pass
Financing Receivable, Recorded Investment [Line Items]
2020	153,017
2019	99,440
2018	118,854
2017	83,534
2016	63,477
2015 and Prior	244,852
Revolving	33,467
Total	796,641	790,226
Residential real estate | Nonpass
Financing Receivable, Recorded Investment [Line Items]
Total		42,051
Residential real estate | Watch
Financing Receivable, Recorded Investment [Line Items]
2020	3,986
2019	4,507
2018	2,188
2017	1,896
2016	3,117
2015 and Prior	8,525
Revolving	0
Total	24,219
Residential real estate | Substandard
Financing Receivable, Recorded Investment [Line Items]
2020	980
2019	442
2018	2,507
2017	1,528
2016	884
2015 and Prior	12,141
Revolving	1,100
Total	19,582
Consumer
Financing Receivable, Recorded Investment [Line Items]
2020	37,686
2019	28,957
2018	21,342
2017	15,874
2016	4,988
2015 and Prior	22,105
Revolving	283,440
Total	414,392	443,332
Consumer | Pass
Financing Receivable, Recorded Investment [Line Items]
2020	37,037
2019	27,646
2018	18,811
2017	15,034
2016	4,009
2015 and Prior	19,483
Revolving	280,996
Total	403,016	430,733
Consumer | Nonpass
Financing Receivable, Recorded Investment [Line Items]
Total		$ 12,599
Consumer | Watch
Financing Receivable, Recorded Investment [Line Items]
2020	168
2019	352
2018	647
2017	340
2016	82
2015 and Prior	646
Revolving	1,622
Total	3,857
Consumer | Substandard
Financing Receivable, Recorded Investment [Line Items]
2020	481
2019	959
2018	1,884
2017	500
2016	897
2015 and Prior	1,976
Revolving	822
Total	$ 7,519