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BASIS OF PRESENTATION - Impact of Adoption of the ASU (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Jan. 01, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle
Retained earnings	$ 536,390		$ 529,005
Allowance for credit losses	71,844		61,408	$ 53,609	$ 50,652
ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses		$ 61,408
Commercial and industrial loans
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses	32,052		28,333	24,739	25,789
Commercial and industrial loans \| ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses		28,333
Commercial real estate and multi-family residential loans
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses	29,445		22,907	18,658	15,796
Commercial real estate and multi-family residential loans \| ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses		22,907
Agri-business and agricultural loans
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses	3,901		3,043	3,704	3,869
Agri-business and agricultural loans \| ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses		3,043
Other commercial loans \| ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses		416
Consumer 1-4 family loans
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses	3,384		2,619	2,475	2,086
Consumer 1-4 family loans \| ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses		2,619
Other consumer loans \| ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses		951
Unallocated
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses	$ 597		3,139	$ 3,065	$ 2,320
Unallocated \| ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses		3,139
Impact of ASC 326 Adoption
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses		9,050
Impact of ASC 326 Adoption \| ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses		9,100	9,050
Impact of ASC 326 Adoption \| Commercial and industrial loans
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses		4,312
Impact of ASC 326 Adoption \| Commercial and industrial loans \| ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses			4,312
Impact of ASC 326 Adoption \| Commercial real estate and multi-family residential loans
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses		4,316
Impact of ASC 326 Adoption \| Commercial real estate and multi-family residential loans \| ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses			4,316
Impact of ASC 326 Adoption \| Agri-business and agricultural loans
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses		1,060
Impact of ASC 326 Adoption \| Agri-business and agricultural loans \| ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses			1,060
Impact of ASC 326 Adoption \| Other commercial loans
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses		941
Impact of ASC 326 Adoption \| Consumer 1-4 family loans
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses		953
Impact of ASC 326 Adoption \| Consumer 1-4 family loans \| ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses			953
Impact of ASC 326 Adoption \| Other consumer loans
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses		349
Impact of ASC 326 Adoption \| Unallocated
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses		(2,881)
Impact of ASC 326 Adoption \| Unallocated \| ASU 2016-13
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses			$ (2,881)
As Reported under ASC 326
New Accounting Pronouncements or Change in Accounting Principle
Retained earnings		7,000
Deferred taxes		2,100
Allowance for credit losses		70,458
As Reported under ASC 326 \| Commercial and industrial loans
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses		32,645
As Reported under ASC 326 \| Commercial real estate and multi-family residential loans
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses		27,223
As Reported under ASC 326 \| Agri-business and agricultural loans
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses		4,103
As Reported under ASC 326 \| Other commercial loans
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses		1,357
As Reported under ASC 326 \| Consumer 1-4 family loans
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses		3,572
As Reported under ASC 326 \| Other consumer loans
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses		1,300
As Reported under ASC 326 \| Unallocated
New Accounting Pronouncements or Change in Accounting Principle
Allowance for credit losses		$ 258