ALLOWANCE FOR CREDIT LOSSES AND CREDIT QUALITY - Risk category of loans by loan segment and origination (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Recorded Investment [Line Items]
2021	$ 297,725
2020	1,170,352
2019	547,871
2018	411,470
2017	293,444
Prior	418,144
Term Total	3,139,006
Revolving	1,335,625
Total ending loans balance	4,474,631	$ 4,649,156
Pass
Financing Receivable, Recorded Investment [Line Items]
Total ending loans balance		3,997,245
Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total ending loans balance		251,891
Substandard
Financing Receivable, Recorded Investment [Line Items]
Total ending loans balance		34,264
Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total ending loans balance		0
Not Rated
Financing Receivable, Recorded Investment [Line Items]
Total ending loans balance		365,756
Other consumer loans
Financing Receivable, Recorded Investment [Line Items]
2021	5,676
2020	28,156
2019	13,405
2018	10,166
2017	5,460
Prior	2,004
Term Total	64,867
Revolving	33,968
Total ending loans balance	98,835
Other consumer loans | Pass
Financing Receivable, Recorded Investment [Line Items]
2021	253
2020	6,503
2019	1,687
2018	0
2017	1,395
Prior	0
Term Total	9,838
Revolving	24,887
Total ending loans balance	34,725
Other consumer loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	253
2018	0
2017	0
Prior	0
Term Total	253
Revolving	0
Total ending loans balance	253
Other consumer loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	0
Other consumer loans | Doubtful
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	0
Other consumer loans | Not Rated
Financing Receivable, Recorded Investment [Line Items]
2021	5,423
2020	21,653
2019	11,465
2018	10,166
2017	4,065
Prior	2,004
Term Total	54,776
Revolving	9,081
Total ending loans balance	63,857
Commercial and industrial loans
Financing Receivable, Recorded Investment [Line Items]
Total ending loans balance		1,784,926
Commercial and industrial loans | Working capital lines of credit loans
Financing Receivable, Recorded Investment [Line Items]
2021	1,699
2020	7,903
2019	15,754
2018	2,351
2017	1,341
Prior	677
Term Total	29,725
Revolving	544,971
Total ending loans balance	574,696	626,099
Commercial and industrial loans | Working capital lines of credit loans | Pass
Financing Receivable, Recorded Investment [Line Items]
2021	1,699
2020	7,903
2019	15,719
2018	2,351
2017	1,168
Prior	642
Term Total	29,482
Revolving	469,298
Total ending loans balance	498,780	535,071
Commercial and industrial loans | Working capital lines of credit loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	59,011
Total ending loans balance	59,011	81,095
Commercial and industrial loans | Working capital lines of credit loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	35
2018	0
2017	173
Prior	35
Term Total	243
Revolving	16,662
Total ending loans balance	16,905	9,718
Commercial and industrial loans | Working capital lines of credit loans | Doubtful
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	0	0
Commercial and industrial loans | Working capital lines of credit loans | Not Rated
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	0	215
Commercial and industrial loans | Non-working capital loans
Financing Receivable, Recorded Investment [Line Items]
2021	168,541
2020	462,787
2019	119,112
2018	109,851
2017	45,752
Prior	30,931
Term Total	936,974
Revolving	156,497
Total ending loans balance	1,093,471	1,158,827
Commercial and industrial loans | Non-working capital loans | Pass
Financing Receivable, Recorded Investment [Line Items]
2021	163,261
2020	448,279
2019	115,200
2018	100,782
2017	37,144
Prior	28,151
Term Total	892,817
Revolving	150,459
Total ending loans balance	1,043,276	1,111,989
Commercial and industrial loans | Non-working capital loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
2021	4,424
2020	5,394
2019	1,468
2018	3,302
2017	3,609
Prior	1,635
Term Total	19,832
Revolving	2,896
Total ending loans balance	22,728	26,523
Commercial and industrial loans | Non-working capital loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	6,754
2019	1,340
2018	4,684
2017	4,642
Prior	1,076
Term Total	18,496
Revolving	3,142
Total ending loans balance	21,638	14,820
Commercial and industrial loans | Non-working capital loans | Doubtful
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	0	0
Commercial and industrial loans | Non-working capital loans | Not Rated
Financing Receivable, Recorded Investment [Line Items]
2021	856
2020	2,360
2019	1,104
2018	1,083
2017	357
Prior	69
Term Total	5,829
Revolving	0
Total ending loans balance	5,829	5,495
Commercial real estate and multi-family residential loans
Financing Receivable, Recorded Investment [Line Items]
Total ending loans balance		1,892,572
Commercial real estate and multi-family residential loans | Construction and land development loans
Financing Receivable, Recorded Investment [Line Items]
2021	4,739
2020	36,704
2019	12,586
2018	57,515
2017	1,639
Prior	17,070
Term Total	130,253
Revolving	239,380
Total ending loans balance	369,633	361,664
Commercial real estate and multi-family residential loans | Construction and land development loans | Pass
Financing Receivable, Recorded Investment [Line Items]
2021	4,739
2020	36,704
2019	12,586
2018	57,515
2017	1,639
Prior	17,070
Term Total	130,253
Revolving	239,380
Total ending loans balance	369,633	361,664
Commercial real estate and multi-family residential loans | Construction and land development loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	0	0
Commercial real estate and multi-family residential loans | Construction and land development loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	0	0
Commercial real estate and multi-family residential loans | Construction and land development loans | Doubtful
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	0	0
Commercial real estate and multi-family residential loans | Construction and land development loans | Not Rated
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	0	0
Commercial real estate and multi-family residential loans | Owner occupied loans
Financing Receivable, Recorded Investment [Line Items]
2021	46,376
2020	183,063
2019	75,505
2018	89,309
2017	111,042
Prior	119,609
Term Total	624,904
Revolving	44,030
Total ending loans balance	668,934	647,574
Commercial real estate and multi-family residential loans | Owner occupied loans | Pass
Financing Receivable, Recorded Investment [Line Items]
2021	44,701
2020	181,024
2019	72,230
2018	85,797
2017	86,522
Prior	116,435
Term Total	586,709
Revolving	44,030
Total ending loans balance	630,739	608,845
Commercial real estate and multi-family residential loans | Owner occupied loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
2021	1,675
2020	0
2019	2,183
2018	1,401
2017	23,062
Prior	2,242
Term Total	30,563
Revolving	0
Total ending loans balance	30,563	31,355
Commercial real estate and multi-family residential loans | Owner occupied loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	2,039
2019	1,092
2018	2,111
2017	1,458
Prior	932
Term Total	7,632
Revolving	0
Total ending loans balance	7,632	7,374
Commercial real estate and multi-family residential loans | Owner occupied loans | Doubtful
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	0	0
Commercial real estate and multi-family residential loans | Owner occupied loans | Not Rated
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	0	0
Commercial real estate and multi-family residential loans | Nonowner Occupied Loans
Financing Receivable, Recorded Investment [Line Items]
2021	26,222
2020	168,765
2019	159,073
2018	48,498
2017	43,415
Prior	122,585
Term Total	568,558
Revolving	36,478
Total ending loans balance	605,036	579,050
Commercial real estate and multi-family residential loans | Nonowner Occupied Loans | Pass
Financing Receivable, Recorded Investment [Line Items]
2021	26,222
2020	168,765
2019	158,407
2018	45,092
2017	43,415
Prior	95,478
Term Total	537,379
Revolving	36,478
Total ending loans balance	573,857	547,790
Commercial real estate and multi-family residential loans | Nonowner Occupied Loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	666
2018	3,406
2017	0
Prior	27,107
Term Total	31,179
Revolving	0
Total ending loans balance	31,179	31,260
Commercial real estate and multi-family residential loans | Nonowner Occupied Loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	0	0
Commercial real estate and multi-family residential loans | Nonowner Occupied Loans | Doubtful
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	0	0
Commercial real estate and multi-family residential loans | Nonowner Occupied Loans | Not Rated
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	0	0
Commercial real estate and multi-family residential loans | Multifamily Loans
Financing Receivable, Recorded Investment [Line Items]
2021	13,224
2020	109,440
2019	79,629
2018	14,830
2017	39,494
Prior	30,423
Term Total	287,040
Revolving	13,956
Total ending loans balance	300,996	304,284
Commercial real estate and multi-family residential loans | Multifamily Loans | Pass
Financing Receivable, Recorded Investment [Line Items]
2021	13,224
2020	109,440
2019	79,629
2018	14,830
2017	17,242
Prior	30,423
Term Total	264,788
Revolving	13,956
Total ending loans balance	278,744	282,031
Commercial real estate and multi-family residential loans | Multifamily Loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	22,252
Prior	0
Term Total	22,252
Revolving	0
Total ending loans balance	22,252	22,253
Commercial real estate and multi-family residential loans | Multifamily Loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	0	0
Commercial real estate and multi-family residential loans | Multifamily Loans | Doubtful
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	0	0
Commercial real estate and multi-family residential loans | Multifamily Loans | Not Rated
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	0	0
Agri-business and agricultural loans
Financing Receivable, Recorded Investment [Line Items]
Total ending loans balance		429,662
Agri-business and agricultural loans | Loans Secured By Farmland
Financing Receivable, Recorded Investment [Line Items]
2021	16,709
2020	34,254
2019	24,018
2018	16,563
2017	11,633
Prior	27,786
Term Total	130,963
Revolving	23,823
Total ending loans balance	154,786	195,363
Agri-business and agricultural loans | Loans Secured By Farmland | Pass
Financing Receivable, Recorded Investment [Line Items]
2021	16,709
2020	31,945
2019	21,644
2018	15,817
2017	11,433
Prior	25,434
Term Total	122,982
Revolving	21,195
Total ending loans balance	144,177	183,983
Agri-business and agricultural loans | Loans Secured By Farmland | Special Mention
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	2,089
2019	2,374
2018	746
2017	200
Prior	1,924
Term Total	7,333
Revolving	2,628
Total ending loans balance	9,961	10,728
Agri-business and agricultural loans | Loans Secured By Farmland | Substandard
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	220
2019	0
2018	0
2017	0
Prior	428
Term Total	648
Revolving	0
Total ending loans balance	648	652
Agri-business and agricultural loans | Loans Secured By Farmland | Doubtful
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	0	0
Agri-business and agricultural loans | Loans Secured By Farmland | Not Rated
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	0	0
Agri-business and agricultural loans | Loans For Agricultural Production
Financing Receivable, Recorded Investment [Line Items]
2021	2,089
2020	43,703
2019	11,056
2018	31,090
2017	1,913
Prior	8,467
Term Total	98,318
Revolving	94,094
Total ending loans balance	192,412	234,299
Agri-business and agricultural loans | Loans For Agricultural Production | Pass
Financing Receivable, Recorded Investment [Line Items]
2021	1,594
2020	33,549
2019	5,474
2018	12,302
2017	1,851
Prior	8,448
Term Total	63,218
Revolving	82,152
Total ending loans balance	145,370	185,875
Agri-business and agricultural loans | Loans For Agricultural Production | Special Mention
Financing Receivable, Recorded Investment [Line Items]
2021	495
2020	10,154
2019	5,582
2018	18,788
2017	62
Prior	19
Term Total	35,100
Revolving	11,942
Total ending loans balance	47,042	48,424
Agri-business and agricultural loans | Loans For Agricultural Production | Substandard
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	0	0
Agri-business and agricultural loans | Loans For Agricultural Production | Doubtful
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	0	0
Agri-business and agricultural loans | Loans For Agricultural Production | Not Rated
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	0	0
Other Commercial
Financing Receivable, Recorded Investment [Line Items]
Total ending loans balance		93,912
Consumer 1-4 family loans
Financing Receivable, Recorded Investment [Line Items]
Total ending loans balance		344,699
Consumer 1-4 family loans | Closed end first mortgage loans
Financing Receivable, Recorded Investment [Line Items]
2021	7,726
2020	50,820
2019	21,413
2018	20,207
2017	17,185
Prior	40,541
Term Total	157,892
Revolving	3,348
Total ending loans balance	161,240	167,501
Consumer 1-4 family loans | Closed end first mortgage loans | Pass
Financing Receivable, Recorded Investment [Line Items]
2021	3,252
2020	18,893
2019	7,016
2018	7,339
2017	4,048
Prior	6,407
Term Total	46,955
Revolving	2,717
Total ending loans balance	49,672	40,682
Consumer 1-4 family loans | Closed end first mortgage loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	0	0
Consumer 1-4 family loans | Closed end first mortgage loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	14
Prior	1,481
Term Total	1,495
Revolving	0
Total ending loans balance	1,495	1,695
Consumer 1-4 family loans | Closed end first mortgage loans | Doubtful
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	0	0
Consumer 1-4 family loans | Closed end first mortgage loans | Not Rated
Financing Receivable, Recorded Investment [Line Items]
2021	4,474
2020	31,927
2019	14,397
2018	12,868
2017	13,123
Prior	32,653
Term Total	109,442
Revolving	631
Total ending loans balance	110,073	125,124
Consumer 1-4 family loans | Open end and junior lien loans
Financing Receivable, Recorded Investment [Line Items]
2021	1,666
2020	9,802
2019	9,456
2018	8,304
2017	4,119
Prior	2,635
Term Total	35,982
Revolving	123,052
Total ending loans balance	159,034	165,236
Consumer 1-4 family loans | Open end and junior lien loans | Pass
Financing Receivable, Recorded Investment [Line Items]
2021	101
2020	494
2019	166
2018	404
2017	0
Prior	32
Term Total	1,197
Revolving	10,305
Total ending loans balance	11,502	8,424
Consumer 1-4 family loans | Open end and junior lien loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	0	0
Consumer 1-4 family loans | Open end and junior lien loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	0	5
Consumer 1-4 family loans | Open end and junior lien loans | Doubtful
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	0	0
Consumer 1-4 family loans | Open end and junior lien loans | Not Rated
Financing Receivable, Recorded Investment [Line Items]
2021	1,565
2020	9,308
2019	9,290
2018	7,900
2017	4,119
Prior	2,603
Term Total	34,785
Revolving	112,747
Total ending loans balance	147,532	156,807
Consumer 1-4 family loans | Residential construction loans
Financing Receivable, Recorded Investment [Line Items]
2021	2,139
2020	4,268
2019	1,098
2018	262
2017	202
Prior	1,210
Term Total	9,179
Revolving	0
Total ending loans balance	9,179	11,962
Consumer 1-4 family loans | Residential construction loans | Pass
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	0	0
Consumer 1-4 family loans | Residential construction loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	0	0
Consumer 1-4 family loans | Residential construction loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	0	0
Consumer 1-4 family loans | Residential construction loans | Doubtful
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	0	0
Consumer 1-4 family loans | Residential construction loans | Not Rated
Financing Receivable, Recorded Investment [Line Items]
2021	2,139
2020	4,268
2019	1,098
2018	262
2017	202
Prior	1,210
Term Total	9,179
Revolving	0
Total ending loans balance	9,179	11,962
Consumer 1-4 family loans | Other consumer loans
Financing Receivable, Recorded Investment [Line Items]
Total ending loans balance		103,385
Other Consumer
Financing Receivable, Recorded Investment [Line Items]
Total ending loans balance		103,385
Unallocated
Financing Receivable, Recorded Investment [Line Items]
Total ending loans balance		$ 0
Other commercial loans
Financing Receivable, Recorded Investment [Line Items]
2021	919
2020	30,687
2019	5,766
2018	2,524
2017	10,249
Prior	14,206
Term Total	64,351
Revolving	22,028
Total ending loans balance	86,379
Other commercial loans | Pass
Financing Receivable, Recorded Investment [Line Items]
2021	919
2020	30,687
2019	5,766
2018	2,524
2017	10,249
Prior	14,206
Term Total	64,351
Revolving	22,028
Total ending loans balance	86,379
Other commercial loans | Special Mention
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	0
Other commercial loans | Substandard
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	0
Other commercial loans | Doubtful
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	0
Other commercial loans | Not Rated
Financing Receivable, Recorded Investment [Line Items]
2021	0
2020	0
2019	0
2018	0
2017	0
Prior	0
Term Total	0
Revolving	0
Total ending loans balance	$ 0