LOANS - Total Loans Outstanding (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable before allowance for credit loss	$ 4,356,471	$ 4,291,105
Percentage of loans receivable	100.00%	100.00%
Less: Allowance for credit losses	$ (67,526)	$ (67,773)	$ (71,844)	$ (61,408)
Net deferred loan fees	(2,757)	(3,264)
Loans, net	4,286,188	4,220,068
Total commercial loans | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable before allowance for credit loss	$ 3,922,910	$ 3,863,630
Percentage of loans receivable	90.10%	90.10%
Total consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable before allowance for credit loss	$ 433,561	$ 427,475
Percentage of loans receivable	9.90%	9.90%
Other consumer loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable before allowance for credit loss	$ 83,395	$ 82,755
Percentage of loans receivable	1.90%	1.90%
Commercial and industrial loans:
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable before allowance for credit loss	$ 1,463,457	$ 1,389,469
Percentage of loans receivable	33.60%	32.40%
Commercial and industrial loans: | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Less: Allowance for credit losses	$ (31,322)	$ (30,595)	(32,052)	(28,333)
Commercial and industrial loans: | Working capital lines of credit loans | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable before allowance for credit loss	$ 678,567	$ 652,861
Percentage of loans receivable	15.60%	15.20%
Commercial and industrial loans: | Non-working capital loans | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable before allowance for credit loss	$ 784,890	$ 736,608
Percentage of loans receivable	18.00%	17.20%
Commercial real estate and multi-family residential loans:
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable before allowance for credit loss	$ 1,957,372	$ 1,954,846
Percentage of loans receivable	44.90%	45.60%
Commercial real estate and multi-family residential loans: | Construction and land development loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable before allowance for credit loss	$ 399,618	$ 379,813
Percentage of loans receivable	9.20%	8.90%
Commercial real estate and multi-family residential loans: | Owner occupied loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable before allowance for credit loss	$ 724,588	$ 739,371
Percentage of loans receivable	16.60%	17.20%
Commercial real estate and multi-family residential loans: | Nonowner occupied loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable before allowance for credit loss	$ 619,163	$ 588,458
Percentage of loans receivable	14.20%	13.70%
Commercial real estate and multi-family residential loans: | Multifamily loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable before allowance for credit loss	$ 214,003	$ 247,204
Percentage of loans receivable	4.90%	5.80%
Agri-business and agricultural loans:
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable before allowance for credit loss	$ 423,669	$ 445,825
Percentage of loans receivable	9.80%	10.40%
Agri-business and agricultural loans: | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Less: Allowance for credit losses	$ (4,761)	$ (5,034)	$ (3,901)	$ (3,043)
Agri-business and agricultural loans: | Loans secured by farmland | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable before allowance for credit loss	$ 164,252	$ 206,331
Percentage of loans receivable	3.80%	4.80%
Agri-business and agricultural loans: | Loans for agricultural production | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable before allowance for credit loss	$ 259,417	$ 239,494
Percentage of loans receivable	6.00%	5.60%
Other commercial loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable before allowance for credit loss	$ 78,412	$ 73,490
Percentage of loans receivable	1.80%	1.70%
Consumer 1-4 family mortgage loans:
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable before allowance for credit loss	$ 350,166	$ 344,720
Percentage of loans receivable	8.00%	8.00%
Consumer 1-4 family mortgage loans: | Closed end first mortgage loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable before allowance for credit loss	$ 180,448	$ 176,561
Percentage of loans receivable	4.10%	4.10%
Consumer 1-4 family mortgage loans: | Open end and junior lien loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable before allowance for credit loss	$ 158,583	$ 156,238
Percentage of loans receivable	3.60%	3.60%
Consumer 1-4 family mortgage loans: | Residential construction and land development loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable before allowance for credit loss	$ 11,135	$ 11,921
Percentage of loans receivable	0.30%	0.30%