LOANS (Loans by credit quality indicator) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	$ 2,682,523	$ 3,119,680
Year Two	1,807,056	1,842,640
Year Three	1,407,474	1,287,023
Year Four	870,616	842,221
Year Five	645,781	485,454
Year Six and Prior	1,250,873	1,254,784
Revolving	1,190,584	1,191,249
Total	9,854,907	10,023,051
Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	2,555,629	2,847,203
Year Two	1,679,770	1,649,219
Year Three	1,249,457	1,131,756
Year Four	715,272	727,712
Year Five	570,128	408,380
Year Six and Prior	1,074,513	1,091,908
Revolving	1,108,787	1,084,202
Total	8,953,556	8,940,380
Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	57,811	129,037
Year Two	75,614	141,385
Year Three	98,095	80,970
Year Four	117,743	58,813
Year Five	30,611	44,512
Year Six and Prior	70,952	76,144
Revolving	40,349	74,056
Total	491,175	604,917
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	69,083	143,440
Year Two	51,672	52,036
Year Three	59,922	74,297
Year Four	37,601	55,696
Year Five	45,042	32,562
Year Six and Prior	105,408	86,732
Revolving	41,448	32,991
Total	410,176	477,754
Commercial and industrial | Commercial and industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	488,043	622,451
Year Two	425,017	381,759
Year Three	268,350	197,442
Year Four	120,928	245,675
Year Five	196,484	118,180
Year Six and Prior	376,816	359,845
Revolving	662,731	609,447
Total	2,538,369	2,534,799
Commercial and industrial | Commercial and industrial | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	460,258	557,853
Year Two	401,606	340,809
Year Three	239,419	168,873
Year Four	100,840	215,696
Year Five	179,241	101,010
Year Six and Prior	343,238	337,834
Revolving	602,155	541,627
Total	2,326,757	2,263,702
Commercial and industrial | Commercial and industrial | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	13,274	41,574
Year Two	14,096	24,676
Year Three	13,982	19,672
Year Four	11,230	14,262
Year Five	6,363	8,072
Year Six and Prior	16,657	2,474
Revolving	30,157	49,432
Total	105,759	160,162
Commercial and industrial | Commercial and industrial | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	14,511	23,024
Year Two	9,315	16,274
Year Three	14,949	8,897
Year Four	8,858	15,717
Year Five	10,880	9,098
Year Six and Prior	16,921	19,537
Revolving	30,419	18,388
Total	105,853	110,935
Commercial and industrial | Paycheck Protection Program ("PPP")
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	336,308	957,785
Year Two	72,939	0
Year Three	0	0
Year Four	0	0
Year Five	0	0
Year Six and Prior	0	0
Revolving	0	0
Total	409,247	957,785
Commercial and industrial | Paycheck Protection Program ("PPP") | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	297,218	880,709
Year Two	59,481	0
Year Three	0	0
Year Four	0	0
Year Five	0	0
Year Six and Prior	0	0
Revolving	0	0
Total	356,699	880,709
Commercial and industrial | Paycheck Protection Program ("PPP") | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	19,656	22,533
Year Two	11,210	0
Year Three	0	0
Year Four	0	0
Year Five	0	0
Year Six and Prior	0	0
Revolving	0	0
Total	30,866	22,533
Commercial and industrial | Paycheck Protection Program ("PPP") | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	19,434	54,543
Year Two	2,248	0
Year Three	0	0
Year Four	0	0
Year Five	0	0
Year Six and Prior	0	0
Revolving	0	0
Total	21,682	54,543
Commercial and industrial | Owner occupied commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	686,705	431,921
Year Two	412,865	392,687
Year Three	364,187	334,894
Year Four	229,112	202,428
Year Five	158,448	124,531
Year Six and Prior	250,861	250,770
Revolving	33,049	39,175
Total	2,135,227	1,776,406
Commercial and industrial | Owner occupied commercial real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	679,698	400,662
Year Two	378,366	369,401
Year Three	337,572	300,242
Year Four	207,982	167,470
Year Five	128,973	107,234
Year Six and Prior	220,013	213,780
Revolving	29,446	33,759
Total	1,982,050	1,592,548
Commercial and industrial | Owner occupied commercial real estate | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	2,517	15,345
Year Two	16,981	13,764
Year Three	13,277	22,488
Year Four	18,264	20,811
Year Five	15,618	8,717
Year Six and Prior	9,216	15,282
Revolving	1,853	4,311
Total	77,726	100,718
Commercial and industrial | Owner occupied commercial real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	4,490	15,914
Year Two	17,518	9,522
Year Three	13,338	12,164
Year Four	2,866	14,147
Year Five	13,857	8,580
Year Six and Prior	21,632	21,708
Revolving	1,750	1,105
Total	75,451	83,140
Commercial and industrial | Non-owner occupied commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	425,727	388,447
Year Two	349,453	481,561
Year Three	423,480	353,464
Year Four	312,544	229,871
Year Five	188,566	138,171
Year Six and Prior	282,891	299,885
Revolving	37,826	30,082
Total	2,020,487	1,921,481
Commercial and industrial | Non-owner occupied commercial real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	394,782	334,722
Year Two	316,992	411,301
Year Three	353,092	305,456
Year Four	274,618	194,101
Year Five	166,123	108,070
Year Six and Prior	199,072	233,153
Revolving	37,518	24,466
Total	1,742,197	1,611,269
Commercial and industrial | Non-owner occupied commercial real estate | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	12,832	22,826
Year Two	17,170	55,225
Year Three	48,377	24,718
Year Four	35,098	18,724
Year Five	7,595	20,954
Year Six and Prior	35,783	45,672
Revolving	0	5,114
Total	156,855	193,233
Commercial and industrial | Non-owner occupied commercial real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	18,113	30,899
Year Two	15,291	15,035
Year Three	22,011	23,290
Year Four	2,828	17,046
Year Five	14,848	9,147
Year Six and Prior	48,036	21,060
Revolving	308	502
Total	121,435	116,979
Commercial and industrial | Real estate construction
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	242,239	313,926
Year Two	282,949	339,097
Year Three	192,647	161,610
Year Four	64,487	12,957
Year Five	8,501	7,048
Year Six and Prior	9,797	5,856
Revolving	13,381	22,726
Total	814,001	863,220
Commercial and industrial | Real estate construction | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	240,048	311,625
Year Two	282,023	309,678
Year Three	177,594	157,171
Year Four	15,228	12,625
Year Five	8,501	6,954
Year Six and Prior	9,628	5,110
Revolving	13,269	21,431
Total	746,291	824,594
Commercial and industrial | Real estate construction | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	2,191	2,105
Year Two	876	26,659
Year Three	15,006	2,403
Year Four	47,267	332
Year Five	0	55
Year Six and Prior	0	388
Revolving	112	1,295
Total	65,452	33,237
Commercial and industrial | Real estate construction | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	0	196
Year Two	50	2,760
Year Three	47	2,036
Year Four	1,992	0
Year Five	0	39
Year Six and Prior	169	358
Revolving	0	0
Total	2,258	5,389
Agricultural and agricultural real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	186,916	209,481
Year Two	131,717	114,190
Year Three	81,406	94,722
Year Four	59,019	48,458
Year Five	28,726	25,058
Year Six and Prior	53,016	50,805
Revolving	143,870	171,812
Total	684,670	714,526
Agricultural and agricultural real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	174,014	171,578
Year Two	114,928	90,944
Year Three	66,869	62,349
Year Four	37,763	39,252
Year Five	24,751	17,626
Year Six and Prior	39,479	37,696
Revolving	128,684	148,456
Total	586,488	567,901
Agricultural and agricultural real estate | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	5,343	20,500
Year Two	10,435	16,202
Year Three	5,967	8,854
Year Four	3,013	2,448
Year Five	38	3,515
Year Six and Prior	3,711	3,157
Revolving	6,840	12,282
Total	35,347	66,958
Agricultural and agricultural real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	7,559	17,403
Year Two	6,354	7,044
Year Three	8,570	23,519
Year Four	18,243	6,758
Year Five	3,937	3,917
Year Six and Prior	9,826	9,952
Revolving	8,346	11,074
Total	62,835	79,667
Residential real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	257,102	157,983
Year Two	108,716	104,389
Year Three	59,880	123,549
Year Four	72,609	86,958
Year Five	52,809	67,478
Year Six and Prior	256,766	265,518
Revolving	32,474	34,567
Total	840,356	840,442
Residential real estate | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	251,931	153,017
Year Two	103,529	99,440
Year Three	58,179	118,854
Year Four	68,551	83,534
Year Five	50,817	63,477
Year Six and Prior	244,641	244,852
Revolving	32,474	33,467
Total	810,122	796,641
Residential real estate | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	1,086	3,986
Year Two	4,650	4,507
Year Three	1,205	2,188
Year Four	1,503	1,896
Year Five	807	3,117
Year Six and Prior	5,043	8,525
Revolving	0	0
Total	14,294	24,219
Residential real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	4,085	980
Year Two	537	442
Year Three	496	2,507
Year Four	2,555	1,528
Year Five	1,185	884
Year Six and Prior	7,082	12,141
Revolving	0	1,100
Total	15,940	19,582
Consumer
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	59,483	37,686
Year Two	23,400	28,957
Year Three	17,524	21,342
Year Four	11,917	15,874
Year Five	12,247	4,988
Year Six and Prior	20,726	22,105
Revolving	267,253	283,440
Total	412,550	414,392
Consumer | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	57,680	37,037
Year Two	22,845	27,646
Year Three	16,732	18,811
Year Four	10,290	15,034
Year Five	11,722	4,009
Year Six and Prior	18,442	19,483
Revolving	265,241	280,996
Total	402,952	403,016
Consumer | Watch
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	912	168
Year Two	196	352
Year Three	281	647
Year Four	1,368	340
Year Five	190	82
Year Six and Prior	542	646
Revolving	1,387	1,622
Total	4,876	3,857
Consumer | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Year One	891	481
Year Two	359	959
Year Three	511	1,884
Year Four	259	500
Year Five	335	897
Year Six and Prior	1,742	1,976
Revolving	625	822
Total	$ 4,722	$ 7,519