ALLOWANCE FOR CREDIT LOSSES AND CREDIT QUALITY - Risk category of loans by loan segment and origination (Details) $ in Thousands	Sep. 30, 2021 USD ($)
Financing Receivable, Credit Quality Indicator [Line Items]
2021	$ 655,420
2020	800,955
2019	456,315
2018	302,775
2017	241,581
Prior	323,468
Term Total	2,780,514
Revolving	1,458,939
Total	4,239,453
Other consumer loans
Financing Receivable, Credit Quality Indicator [Line Items]
2021	18,882
2020	18,239
2019	10,514
2018	6,945
2017	3,784
Prior	1,418
Term Total	59,782
Revolving	32,165
Total	91,947
Other consumer loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2021	584
2020	1,181
2019	1,579
2018	0
2017	1,253
Prior	0
Term Total	4,597
Revolving	22,084
Total	26,681
Other consumer loans | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2021	36
2020	0
2019	257
2018	0
2017	0
Prior	0
Term Total	293
Revolving	0
Total	293
Other consumer loans | Not Rated
Financing Receivable, Credit Quality Indicator [Line Items]
2021	18,262
2020	17,058
2019	8,678
2018	6,945
2017	2,531
Prior	1,418
Term Total	54,892
Revolving	10,081
Total	64,973
Commercial and industrial loans | Working capital lines of credit loans
Financing Receivable, Credit Quality Indicator [Line Items]
2021	8,755
2020	6,467
2019	11,728
2018	1,646
2017	834
Prior	82
Term Total	29,512
Revolving	629,762
Total	659,274
Commercial and industrial loans | Working capital lines of credit loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2021	8,755
2020	6,467
2019	11,643
2018	1,646
2017	834
Prior	82
Term Total	29,427
Revolving	533,140
Total	562,567
Commercial and industrial loans | Working capital lines of credit loans | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	64,240
Total	64,240
Commercial and industrial loans | Working capital lines of credit loans | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	0
2019	85
2018	0
2017	0
Prior	0
Term Total	85
Revolving	32,382
Total	32,467
Commercial and industrial loans | Non-working capital loans
Financing Receivable, Credit Quality Indicator [Line Items]
2021	208,503
2020	181,762
2019	90,667
2018	75,326
2017	32,093
Prior	22,267
Term Total	610,618
Revolving	169,047
Total	779,665
Commercial and industrial loans | Non-working capital loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2021	184,286
2020	172,825
2019	87,892
2018	68,814
2017	23,713
Prior	20,548
Term Total	558,078
Revolving	163,413
Total	721,491
Commercial and industrial loans | Non-working capital loans | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2021	17,614
2020	0
2019	630
2018	1,112
2017	2,466
Prior	1,185
Term Total	23,007
Revolving	2,426
Total	25,433
Commercial and industrial loans | Non-working capital loans | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2021	4,908
2020	7,022
2019	1,225
2018	4,681
2017	5,723
Prior	512
Term Total	24,071
Revolving	3,208
Total	27,279
Commercial and industrial loans | Non-working capital loans | Not Rated
Financing Receivable, Credit Quality Indicator [Line Items]
2021	1,695
2020	1,915
2019	920
2018	719
2017	191
Prior	22
Term Total	5,462
Revolving	0
Total	5,462
Commercial real estate and multi-family residential loans | Construction and land development loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2021	13,305
2020	40,841
2019	4,679
2018	30,875
2017	0
Prior	16,870
Term Total	106,570
Revolving	270,801
Total	377,371
Commercial real estate and multi-family residential loans | Owner occupied loans
Financing Receivable, Credit Quality Indicator [Line Items]
2021	101,124
2020	176,552
2019	130,311
2018	97,920
2017	90,861
Prior	107,251
Term Total	704,019
Revolving	36,226
Total	740,245
Commercial real estate and multi-family residential loans | Owner occupied loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2021	93,789
2020	174,606
2019	127,573
2018	94,853
2017	82,439
Prior	105,570
Term Total	678,830
Revolving	36,226
Total	715,056
Commercial real estate and multi-family residential loans | Owner occupied loans | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2021	6,829
2020	0
2019	1,809
2018	966
2017	7,715
Prior	1,273
Term Total	18,592
Revolving	0
Total	18,592
Commercial real estate and multi-family residential loans | Owner occupied loans | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2021	506
2020	1,946
2019	929
2018	2,101
2017	707
Prior	408
Term Total	6,597
Revolving	0
Total	6,597
Commercial real estate and multi-family residential loans | Nonowner occupied loans
Financing Receivable, Credit Quality Indicator [Line Items]
2021	87,697
2020	160,901
2019	118,953
2018	29,996
2017	41,494
Prior	83,470
Term Total	522,511
Revolving	59,107
Total	581,618
Commercial real estate and multi-family residential loans | Nonowner occupied loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2021	75,760
2020	160,552
2019	118,333
2018	26,642
2017	41,494
Prior	69,129
Term Total	491,910
Revolving	59,107
Total	551,017
Commercial real estate and multi-family residential loans | Nonowner occupied loans | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2021	11,937
2020	349
2019	620
2018	0
2017	0
Prior	14,341
Term Total	27,247
Revolving	0
Total	27,247
Commercial real estate and multi-family residential loans | Nonowner occupied loans | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	0
2019	0
2018	3,354
2017	0
Prior	0
Term Total	3,354
Revolving	0
Total	3,354
Commercial real estate and multi-family residential loans | Multifamily loans
Financing Receivable, Credit Quality Indicator [Line Items]
2021	79,260
2020	53,500
2019	36,784
2018	14,372
2017	36,940
Prior	18,696
Term Total	239,552
Revolving	12,997
Total	252,549
Commercial real estate and multi-family residential loans | Multifamily loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2021	79,260
2020	53,500
2019	36,784
2018	14,372
2017	14,688
Prior	18,696
Term Total	217,300
Revolving	12,997
Total	230,297
Commercial real estate and multi-family residential loans | Multifamily loans | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	22,252
Prior	0
Term Total	22,252
Revolving	0
Total	22,252
Agri-business and agricultural loans | Loans secured by farmland
Financing Receivable, Credit Quality Indicator [Line Items]
2021	35,760
2020	39,839
2019	19,869
2018	13,327
2017	10,031
Prior	19,951
Term Total	138,777
Revolving	13,283
Total	152,060
Agri-business and agricultural loans | Loans secured by farmland | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2021	35,548
2020	37,854
2019	17,533
2018	13,327
2017	9,841
Prior	19,776
Term Total	133,879
Revolving	12,345
Total	146,224
Agri-business and agricultural loans | Loans secured by farmland | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	1,985
2019	2,336
2018	0
2017	190
Prior	30
Term Total	4,541
Revolving	938
Total	5,479
Agri-business and agricultural loans | Loans secured by farmland | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2021	212
2020	0
2019	0
2018	0
2017	0
Prior	145
Term Total	357
Revolving	0
Total	357
Agri-business and agricultural loans | Loans for agricultural production
Financing Receivable, Credit Quality Indicator [Line Items]
2021	27,580
2020	36,603
2019	5,665
2018	11,399
2017	1,521
Prior	4,412
Term Total	87,180
Revolving	84,874
Total	172,054
Agri-business and agricultural loans | Loans for agricultural production | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2021	27,116
2020	27,959
2019	4,415
2018	11,399
2017	1,478
Prior	4,393
Term Total	76,760
Revolving	76,860
Total	153,620
Agri-business and agricultural loans | Loans for agricultural production | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2021	464
2020	8,644
2019	1,250
2018	0
2017	43
Prior	19
Term Total	10,420
Revolving	8,014
Total	18,434
Other commercial loans
Financing Receivable, Credit Quality Indicator [Line Items]
2021	1,488
2020	30,130
2019	3,541
2018	1,328
2017	8,897
Prior	12,717
Term Total	58,101
Revolving	25,162
Total	83,263
Other commercial loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2021	1,488
2020	30,130
2019	3,541
2018	1,328
2017	8,897
Prior	8,772
Term Total	54,156
Revolving	25,162
Total	79,318
Other commercial loans | Special Mention
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	3,945
Term Total	3,945
Revolving	0
Total	3,945
Consumer 1-4 family loans | Closed end first mortgage loans
Financing Receivable, Credit Quality Indicator [Line Items]
2021	48,497
2020	46,168
2019	15,575
2018	14,370
2017	12,559
Prior	33,479
Term Total	170,648
Revolving	2,745
Total	173,393
Consumer 1-4 family loans | Closed end first mortgage loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2021	13,332
2020	17,484
2019	5,487
2018	6,502
2017	3,216
Prior	2,145
Term Total	48,166
Revolving	2,183
Total	50,349
Consumer 1-4 family loans | Closed end first mortgage loans | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	1,821
Term Total	1,821
Revolving	0
Total	1,821
Consumer 1-4 family loans | Closed end first mortgage loans | Not Rated
Financing Receivable, Credit Quality Indicator [Line Items]
2021	35,165
2020	28,684
2019	10,088
2018	7,868
2017	9,343
Prior	29,513
Term Total	120,661
Revolving	562
Total	121,223
Consumer 1-4 family loans | Open end and junior lien loans
Financing Receivable, Credit Quality Indicator [Line Items]
2021	17,405
2020	7,111
2019	7,047
2018	5,131
2017	2,394
Prior	1,678
Term Total	40,766
Revolving	122,757
Total	163,523
Consumer 1-4 family loans | Open end and junior lien loans | Pass
Financing Receivable, Credit Quality Indicator [Line Items]
2021	193
2020	379
2019	162
2018	317
2017	0
Prior	0
Term Total	1,051
Revolving	10,733
Total	11,784
Consumer 1-4 family loans | Open end and junior lien loans | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total	0
Consumer 1-4 family loans | Open end and junior lien loans | Not Rated
Financing Receivable, Credit Quality Indicator [Line Items]
2021	17,212
2020	6,732
2019	6,885
2018	4,814
2017	2,394
Prior	1,678
Term Total	39,715
Revolving	112,024
Total	151,739
Consumer 1-4 family loans | Residential construction loans | Not Rated
Financing Receivable, Credit Quality Indicator [Line Items]
2021	7,164
2020	2,842
2019	982
2018	140
2017	173
Prior	1,177
Term Total	12,478
Revolving	13
Total	$ 12,491