LOANS (Loans by credit quality indicator) (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
2020	$ 2,034,021
2019	1,841,784
2018	1,387,817
2017	948,556
2016	543,956
2015 and Prior	1,371,175
Revolving	1,119,521
Total	9,246,830	$ 8,367,917
Total gross loans receivable held to maturity	9,246,830	8,367,917
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,919,841
2019	1,735,560
2018	1,246,293
2017	829,810
2016	477,218
2015 and Prior	1,264,515
Revolving	1,029,195
Total	8,502,432	7,811,148
Total gross loans receivable held to maturity	8,502,432	7,811,148
Nonpass
Financing Receivable, Credit Quality Indicator [Line Items]
Total		556,769
Total gross loans receivable held to maturity		556,769
Watch
Financing Receivable, Credit Quality Indicator [Line Items]
2020	47,846
2019	76,866
2018	72,110
2017	78,909
2016	41,436
2015 and Prior	38,009
Revolving	58,176
Total	413,352
Total gross loans receivable held to maturity	413,352
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	66,334
2019	29,358
2018	69,414
2017	39,837
2016	25,302
2015 and Prior	68,651
Revolving	32,150
Total	331,046
Total gross loans receivable held to maturity	331,046
Commercial and industrial | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
2020	281,334
2019	442,577
2018	245,920
2017	288,969
2016	150,062
2015 and Prior	368,937
Revolving	586,601
Total	2,364,400	2,530,809
Total gross loans receivable held to maturity	2,364,400	2,530,809
Commercial and industrial | Commercial and industrial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	270,156
2019	395,142
2018	210,947
2017	255,555
2016	130,483
2015 and Prior	356,052
Revolving	523,532
Total	2,141,867	2,352,131
Total gross loans receivable held to maturity	2,141,867	2,352,131
Commercial and industrial | Commercial and industrial | Nonpass
Financing Receivable, Credit Quality Indicator [Line Items]
Total		178,678
Total gross loans receivable held to maturity		178,678
Commercial and industrial | Commercial and industrial | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
2020	7,506
2019	39,383
2018	13,278
2017	18,592
2016	8,429
2015 and Prior	184
Revolving	45,250
Total	132,622
Total gross loans receivable held to maturity	132,622
Commercial and industrial | Commercial and industrial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	3,672
2019	8,052
2018	21,695
2017	14,822
2016	11,150
2015 and Prior	12,701
Revolving	17,819
Total	89,911
Total gross loans receivable held to maturity	89,911
Commercial and industrial | Paycheck Protection Program ("PPP")
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,124,430
2019	0
2018	0
2017	0
2016	0
2015 and Prior	0
Revolving	0
Total	1,124,430	0
Total gross loans receivable held to maturity	1,124,430	0
Commercial and industrial | Paycheck Protection Program ("PPP") | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,071,796
2019	0
2018	0
2017	0
2016	0
2015 and Prior	0
Revolving	0
Total	1,071,796
Total gross loans receivable held to maturity	1,071,796
Commercial and industrial | Paycheck Protection Program ("PPP") | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
2020	30,693
2019	0
2018	0
2017	0
2016	0
2015 and Prior	0
Revolving	0
Total	30,693
Total gross loans receivable held to maturity	30,693
Commercial and industrial | Paycheck Protection Program ("PPP") | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	21,941
2019	0
2018	0
2017	0
2016	0
2015 and Prior	0
Revolving	0
Total	21,941
Total gross loans receivable held to maturity	21,941
Commercial and industrial | Owner occupied commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2020	152,069
2019	321,534
2018	305,790
2017	215,373
2016	133,555
2015 and Prior	273,192
Revolving	31,758
Total	1,433,271	1,472,704
Total gross loans receivable held to maturity	1,433,271	1,472,704
Commercial and industrial | Owner occupied commercial real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	139,436
2019	307,221
2018	277,311
2017	175,702
2016	122,807
2015 and Prior	252,559
Revolving	31,445
Total	1,306,481	1,369,290
Total gross loans receivable held to maturity	1,306,481	1,369,290
Commercial and industrial | Owner occupied commercial real estate | Nonpass
Financing Receivable, Credit Quality Indicator [Line Items]
Total		103,414
Total gross loans receivable held to maturity		103,414
Commercial and industrial | Owner occupied commercial real estate | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
2020	5,865
2019	6,529
2018	5,467
2017	29,782
2016	4,585
2015 and Prior	8,422
Revolving	100
Total	60,750
Total gross loans receivable held to maturity	60,750
Commercial and industrial | Owner occupied commercial real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	6,768
2019	7,784
2018	23,012
2017	9,889
2016	6,163
2015 and Prior	12,211
Revolving	213
Total	66,040
Total gross loans receivable held to maturity	66,040
Commercial and industrial | Non-owner occupied commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2020	194,628
2019	409,360
2018	277,881
2017	199,465
2016	123,375
2015 and Prior	308,708
Revolving	30,206
Total	1,543,623	1,495,877
Total gross loans receivable held to maturity	1,543,623	1,495,877
Commercial and industrial | Non-owner occupied commercial real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	174,914
2019	403,907
2018	249,906
2017	176,422
2016	113,130
2015 and Prior	285,323
Revolving	29,731
Total	1,433,333	1,429,760
Total gross loans receivable held to maturity	1,433,333	1,429,760
Commercial and industrial | Non-owner occupied commercial real estate | Nonpass
Financing Receivable, Credit Quality Indicator [Line Items]
Total		66,117
Total gross loans receivable held to maturity		66,117
Commercial and industrial | Non-owner occupied commercial real estate | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
2020	254
2019	2,520
2018	26,360
2017	17,152
2016	8,868
2015 and Prior	16,265
Revolving	475
Total	71,894
Total gross loans receivable held to maturity	71,894
Commercial and industrial | Non-owner occupied commercial real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	19,460
2019	2,933
2018	1,615
2017	5,891
2016	1,377
2015 and Prior	7,120
Revolving	0
Total	38,396
Total gross loans receivable held to maturity	38,396
Commercial and industrial | Real estate construction
Financing Receivable, Credit Quality Indicator [Line Items]
2020	142,231
2019	442,685
2018	336,244
2017	94,824
2016	49,317
2015 and Prior	33,898
Revolving	16,644
Total	1,115,843	1,027,081
Total gross loans receivable held to maturity	1,115,843	1,027,081
Commercial and industrial | Real estate construction | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	136,140
2019	423,116
2018	314,934
2017	82,944
2016	31,864
2015 and Prior	32,028
Revolving	15,820
Total	1,036,846	984,736
Total gross loans receivable held to maturity	1,036,846	984,736
Commercial and industrial | Real estate construction | Nonpass
Financing Receivable, Credit Quality Indicator [Line Items]
Total		42,345
Total gross loans receivable held to maturity		42,345
Commercial and industrial | Real estate construction | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
2020	329
2019	17,548
2018	20,447
2017	10,418
2016	16,931
2015 and Prior	1,189
Revolving	824
Total	67,686
Total gross loans receivable held to maturity	67,686
Commercial and industrial | Real estate construction | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	5,762
2019	2,021
2018	863
2017	1,462
2016	522
2015 and Prior	681
Revolving	0
Total	11,311
Total gross loans receivable held to maturity	11,311
Agricultural and agricultural real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2020	72,297
2019	106,119
2018	76,211
2017	41,755
2016	23,323
2015 and Prior	58,709
Revolving	142,359
Total	520,773	565,837
Total gross loans receivable held to maturity	520,773	565,837
Agricultural and agricultural real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	60,973
2019	91,129
2018	52,319
2017	34,156
2016	17,330
2015 and Prior	40,204
Revolving	120,864
Total	416,975	454,272
Total gross loans receivable held to maturity	416,975	454,272
Agricultural and agricultural real estate | Nonpass
Financing Receivable, Credit Quality Indicator [Line Items]
Total		111,565
Total gross loans receivable held to maturity		111,565
Agricultural and agricultural real estate | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
2020	3,117
2019	7,501
2018	5,293
2017	1,153
2016	2,027
2015 and Prior	3,914
Revolving	9,307
Total	32,312
Total gross loans receivable held to maturity	32,312
Agricultural and agricultural real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	8,207
2019	7,489
2018	18,599
2017	6,446
2016	3,966
2015 and Prior	14,591
Revolving	12,188
Total	71,486
Total gross loans receivable held to maturity	71,486
Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
2020	47,811
2019	85,933
2018	121,564
2017	91,947
2016	58,452
2015 and Prior	301,397
Revolving	28,658
Total	735,762	832,277
Total gross loans receivable held to maturity	735,762	832,277
Residential real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	47,582
2019	82,571
2018	119,637
2017	89,920
2016	56,886
2015 and Prior	275,367
Revolving	27,211
Total	699,174	790,226
Total gross loans receivable held to maturity	699,174	790,226
Residential real estate | Nonpass
Financing Receivable, Credit Quality Indicator [Line Items]
Total		42,051
Total gross loans receivable held to maturity		42,051
Residential real estate | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
2020	82
2019	3,050
2018	880
2017	1,619
2016	349
2015 and Prior	7,291
Revolving	346
Total	13,617
Total gross loans receivable held to maturity	13,617
Residential real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	147
2019	312
2018	1,047
2017	408
2016	1,217
2015 and Prior	18,739
Revolving	1,101
Total	22,971
Total gross loans receivable held to maturity	22,971
Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
2020	19,221
2019	33,576
2018	24,207
2017	16,223
2016	5,872
2015 and Prior	26,334
Revolving	283,295
Total	408,728	443,332
Total gross loans receivable held to maturity	408,728	443,332
Consumer | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2020	18,844
2019	32,474
2018	21,239
2017	15,111
2016	4,718
2015 and Prior	22,982
Revolving	280,592
Total	395,960	430,733
Total gross loans receivable held to maturity	395,960	430,733
Consumer | Nonpass
Financing Receivable, Credit Quality Indicator [Line Items]
Total		12,599
Total gross loans receivable held to maturity		$ 12,599
Consumer | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	335
2018	385
2017	193
2016	247
2015 and Prior	744
Revolving	1,874
Total	3,778
Total gross loans receivable held to maturity	3,778
Consumer | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	377
2019	767
2018	2,583
2017	919
2016	907
2015 and Prior	2,608
Revolving	829
Total	8,990
Total gross loans receivable held to maturity	$ 8,990