ALLOWANCE FOR CREDIT LOSSES AND CREDIT QUALITY - Credit Quality Indicators (Details) $ in Thousands	Dec. 31, 2020 USD ($)
Financing Receivable, Recorded Investment
Total ending loans balance	$ 4,649,156
Commercial and industrial loans
Financing Receivable, Recorded Investment
Total ending loans balance	1,784,926
Commercial and industrial loans | Working capital lines of credit loans
Financing Receivable, Recorded Investment
Total ending loans balance	626,099
Commercial and industrial loans | Non-working capital loans
Financing Receivable, Recorded Investment
Total ending loans balance	1,158,827
Commercial real estate and multi-family residential loans
Financing Receivable, Recorded Investment
Total ending loans balance	1,892,572
Commercial real estate and multi-family residential loans | Construction and land development loans
Financing Receivable, Recorded Investment
Total ending loans balance	361,664
Commercial real estate and multi-family residential loans | Owner occupied loans
Financing Receivable, Recorded Investment
Total ending loans balance	647,574
Commercial real estate and multi-family residential loans | Nonowner occupied loans
Financing Receivable, Recorded Investment
Total ending loans balance	579,050
Commercial real estate and multi-family residential loans | Multifamily loans
Financing Receivable, Recorded Investment
Total ending loans balance	304,284
Agri-business and agricultural loans
Financing Receivable, Recorded Investment
Total ending loans balance	429,662
Agri-business and agricultural loans | Loans secured by farmland
Financing Receivable, Recorded Investment
Total ending loans balance	195,363
Agri-business and agricultural loans | Loans for agricultural production
Financing Receivable, Recorded Investment
Total ending loans balance	234,299
Agri-business and agricultural loans | Other commercial loans
Financing Receivable, Recorded Investment
Total ending loans balance	93,912
Consumer 1-4 family loans
Financing Receivable, Recorded Investment
Total ending loans balance	344,699
Consumer 1-4 family loans | Closed end first mortgage loans
Financing Receivable, Recorded Investment
Total ending loans balance	167,501
Consumer 1-4 family loans | Open end and junior lien loans
Financing Receivable, Recorded Investment
Total ending loans balance	165,236
Consumer 1-4 family loans | Residential construction loans
Financing Receivable, Recorded Investment
Total ending loans balance	11,962
Consumer 1-4 family loans | Other consumer loans
Financing Receivable, Recorded Investment
Total ending loans balance	103,385
Pass
Financing Receivable, Recorded Investment
Total ending loans balance	3,997,245
Pass | Commercial and industrial loans | Working capital lines of credit loans
Financing Receivable, Recorded Investment
Total ending loans balance	535,071
Pass | Commercial and industrial loans | Non-working capital loans
Financing Receivable, Recorded Investment
Total ending loans balance	1,111,989
Pass | Commercial real estate and multi-family residential loans | Construction and land development loans
Financing Receivable, Recorded Investment
Total ending loans balance	361,664
Pass | Commercial real estate and multi-family residential loans | Owner occupied loans
Financing Receivable, Recorded Investment
Total ending loans balance	608,845
Pass | Commercial real estate and multi-family residential loans | Nonowner occupied loans
Financing Receivable, Recorded Investment
Total ending loans balance	547,790
Pass | Commercial real estate and multi-family residential loans | Multifamily loans
Financing Receivable, Recorded Investment
Total ending loans balance	282,031
Pass | Agri-business and agricultural loans | Loans secured by farmland
Financing Receivable, Recorded Investment
Total ending loans balance	183,983
Pass | Agri-business and agricultural loans | Loans for agricultural production
Financing Receivable, Recorded Investment
Total ending loans balance	185,875
Pass | Agri-business and agricultural loans | Other commercial loans
Financing Receivable, Recorded Investment
Total ending loans balance	93,912
Pass | Consumer 1-4 family loans | Closed end first mortgage loans
Financing Receivable, Recorded Investment
Total ending loans balance	40,682
Pass | Consumer 1-4 family loans | Open end and junior lien loans
Financing Receivable, Recorded Investment
Total ending loans balance	8,424
Pass | Consumer 1-4 family loans | Residential construction loans
Financing Receivable, Recorded Investment
Total ending loans balance	0
Pass | Consumer 1-4 family loans | Other consumer loans
Financing Receivable, Recorded Investment
Total ending loans balance	36,979
Special Mention
Financing Receivable, Recorded Investment
Total ending loans balance	251,891
Special Mention | Commercial and industrial loans | Working capital lines of credit loans
Financing Receivable, Recorded Investment
Total ending loans balance	81,095
Special Mention | Commercial and industrial loans | Non-working capital loans
Financing Receivable, Recorded Investment
Total ending loans balance	26,523
Special Mention | Commercial real estate and multi-family residential loans | Construction and land development loans
Financing Receivable, Recorded Investment
Total ending loans balance	0
Special Mention | Commercial real estate and multi-family residential loans | Owner occupied loans
Financing Receivable, Recorded Investment
Total ending loans balance	31,355
Special Mention | Commercial real estate and multi-family residential loans | Nonowner occupied loans
Financing Receivable, Recorded Investment
Total ending loans balance	31,260
Special Mention | Commercial real estate and multi-family residential loans | Multifamily loans
Financing Receivable, Recorded Investment
Total ending loans balance	22,253
Special Mention | Agri-business and agricultural loans | Loans secured by farmland
Financing Receivable, Recorded Investment
Total ending loans balance	10,728
Special Mention | Agri-business and agricultural loans | Loans for agricultural production
Financing Receivable, Recorded Investment
Total ending loans balance	48,424
Special Mention | Agri-business and agricultural loans | Other commercial loans
Financing Receivable, Recorded Investment
Total ending loans balance	0
Special Mention | Consumer 1-4 family loans | Closed end first mortgage loans
Financing Receivable, Recorded Investment
Total ending loans balance	0
Special Mention | Consumer 1-4 family loans | Open end and junior lien loans
Financing Receivable, Recorded Investment
Total ending loans balance	0
Special Mention | Consumer 1-4 family loans | Residential construction loans
Financing Receivable, Recorded Investment
Total ending loans balance	0
Special Mention | Consumer 1-4 family loans | Other consumer loans
Financing Receivable, Recorded Investment
Total ending loans balance	253
Substandard
Financing Receivable, Recorded Investment
Total ending loans balance	34,264
Substandard | Commercial and industrial loans | Working capital lines of credit loans
Financing Receivable, Recorded Investment
Total ending loans balance	9,718
Substandard | Commercial and industrial loans | Non-working capital loans
Financing Receivable, Recorded Investment
Total ending loans balance	14,820
Substandard | Commercial real estate and multi-family residential loans | Construction and land development loans
Financing Receivable, Recorded Investment
Total ending loans balance	0
Substandard | Commercial real estate and multi-family residential loans | Owner occupied loans
Financing Receivable, Recorded Investment
Total ending loans balance	7,374
Substandard | Commercial real estate and multi-family residential loans | Nonowner occupied loans
Financing Receivable, Recorded Investment
Total ending loans balance	0
Substandard | Commercial real estate and multi-family residential loans | Multifamily loans
Financing Receivable, Recorded Investment
Total ending loans balance	0
Substandard | Agri-business and agricultural loans | Loans secured by farmland
Financing Receivable, Recorded Investment
Total ending loans balance	652
Substandard | Agri-business and agricultural loans | Loans for agricultural production
Financing Receivable, Recorded Investment
Total ending loans balance	0
Substandard | Agri-business and agricultural loans | Other commercial loans
Financing Receivable, Recorded Investment
Total ending loans balance	0
Substandard | Consumer 1-4 family loans | Closed end first mortgage loans
Financing Receivable, Recorded Investment
Total ending loans balance	1,695
Substandard | Consumer 1-4 family loans | Open end and junior lien loans
Financing Receivable, Recorded Investment
Total ending loans balance	5
Substandard | Consumer 1-4 family loans | Residential construction loans
Financing Receivable, Recorded Investment
Total ending loans balance	0
Substandard | Consumer 1-4 family loans | Other consumer loans
Financing Receivable, Recorded Investment
Total ending loans balance	0
Doubtful
Financing Receivable, Recorded Investment
Total ending loans balance	0
Doubtful | Commercial and industrial loans | Working capital lines of credit loans
Financing Receivable, Recorded Investment
Total ending loans balance	0
Doubtful | Commercial and industrial loans | Non-working capital loans
Financing Receivable, Recorded Investment
Total ending loans balance	0
Doubtful | Commercial real estate and multi-family residential loans | Construction and land development loans
Financing Receivable, Recorded Investment
Total ending loans balance	0
Doubtful | Commercial real estate and multi-family residential loans | Owner occupied loans
Financing Receivable, Recorded Investment
Total ending loans balance	0
Doubtful | Commercial real estate and multi-family residential loans | Nonowner occupied loans
Financing Receivable, Recorded Investment
Total ending loans balance	0
Doubtful | Commercial real estate and multi-family residential loans | Multifamily loans
Financing Receivable, Recorded Investment
Total ending loans balance	0
Doubtful | Agri-business and agricultural loans | Loans secured by farmland
Financing Receivable, Recorded Investment
Total ending loans balance	0
Doubtful | Agri-business and agricultural loans | Loans for agricultural production
Financing Receivable, Recorded Investment
Total ending loans balance	0
Doubtful | Agri-business and agricultural loans | Other commercial loans
Financing Receivable, Recorded Investment
Total ending loans balance	0
Doubtful | Consumer 1-4 family loans | Closed end first mortgage loans
Financing Receivable, Recorded Investment
Total ending loans balance	0
Doubtful | Consumer 1-4 family loans | Open end and junior lien loans
Financing Receivable, Recorded Investment
Total ending loans balance	0
Doubtful | Consumer 1-4 family loans | Residential construction loans
Financing Receivable, Recorded Investment
Total ending loans balance	0
Doubtful | Consumer 1-4 family loans | Other consumer loans
Financing Receivable, Recorded Investment
Total ending loans balance	0
Not Rated
Financing Receivable, Recorded Investment
Total ending loans balance	365,756
Not Rated | Commercial and industrial loans | Working capital lines of credit loans
Financing Receivable, Recorded Investment
Total ending loans balance	215
Not Rated | Commercial and industrial loans | Non-working capital loans
Financing Receivable, Recorded Investment
Total ending loans balance	5,495
Not Rated | Commercial real estate and multi-family residential loans | Construction and land development loans
Financing Receivable, Recorded Investment
Total ending loans balance	0
Not Rated | Commercial real estate and multi-family residential loans | Owner occupied loans
Financing Receivable, Recorded Investment
Total ending loans balance	0
Not Rated | Commercial real estate and multi-family residential loans | Nonowner occupied loans
Financing Receivable, Recorded Investment
Total ending loans balance	0
Not Rated | Commercial real estate and multi-family residential loans | Multifamily loans
Financing Receivable, Recorded Investment
Total ending loans balance	0
Not Rated | Agri-business and agricultural loans | Loans secured by farmland
Financing Receivable, Recorded Investment
Total ending loans balance	0
Not Rated | Agri-business and agricultural loans | Loans for agricultural production
Financing Receivable, Recorded Investment
Total ending loans balance	0
Not Rated | Agri-business and agricultural loans | Other commercial loans
Financing Receivable, Recorded Investment
Total ending loans balance	0
Not Rated | Consumer 1-4 family loans | Closed end first mortgage loans
Financing Receivable, Recorded Investment
Total ending loans balance	125,124
Not Rated | Consumer 1-4 family loans | Open end and junior lien loans
Financing Receivable, Recorded Investment
Total ending loans balance	156,807
Not Rated | Consumer 1-4 family loans | Residential construction loans
Financing Receivable, Recorded Investment
Total ending loans balance	11,962
Not Rated | Consumer 1-4 family loans | Other consumer loans
Financing Receivable, Recorded Investment
Total ending loans balance	$ 66,153