LOANS, ALLOWANCE FOR LOAN LOSSES AND IMPAIRED LOANS - Accounts, Notes, Loans and Financing Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Loans receivable
Total Past Due Accruing and Nonaccrual Loans	$ 1,246,889	$ 1,187,264
Performing loans
Loans receivable
TDR loans	11,722	5,370
Other loans	1,223,834	1,161,734
Total Past Due Accruing and Nonaccrual Loans	1,235,556	1,167,104
Nonperforming loans
Loans receivable
TDR loans	6,755	7,224
Other loans	4,578	12,936
Total Past Due Accruing and Nonaccrual Loans	11,333	20,160
Commercial/Agricultural real estate:
Loans receivable
Total Past Due Accruing and Nonaccrual Loans	797,139	773,240
Commercial/Agricultural real estate: | Performing loans
Loans receivable
TDR loans	4,695	1,730
Other loans	786,533	758,237
Total Past Due Accruing and Nonaccrual Loans	791,228	759,967
Commercial/Agricultural real estate: | Nonperforming loans
Loans receivable
TDR loans	4,691	4,868
Other loans	1,220	8,405
Total Past Due Accruing and Nonaccrual Loans	5,911	13,273
C&I/Agricultural operating:
Loans receivable
Total Past Due Accruing and Nonaccrual Loans	273,040	171,514
C&I/Agricultural operating: | Performing loans
Loans receivable
TDR loans	3,836	366
Other loans	266,975	167,596
Total Past Due Accruing and Nonaccrual Loans	270,811	167,962
C&I/Agricultural operating: | Nonperforming loans
Loans receivable
TDR loans	1,287	1,973
Other loans	942	1,579
Total Past Due Accruing and Nonaccrual Loans	2,229	3,552
Residential mortgage:
Loans receivable
Total Past Due Accruing and Nonaccrual Loans	137,646	184,739
Residential mortgage: | Performing loans
Loans receivable
TDR loans	3,142	3,206
Other loans	131,470	178,415
Total Past Due Accruing and Nonaccrual Loans	134,612	181,621
Residential mortgage: | Nonperforming loans
Loans receivable
TDR loans	777	383
Other loans	2,257	2,735
Total Past Due Accruing and Nonaccrual Loans	3,034	3,118
Consumer installment:
Loans receivable
Total Past Due Accruing and Nonaccrual Loans	39,064	57,771
Consumer installment: | Performing loans
Loans receivable
TDR loans	49	68
Other loans	38,856	57,486
Total Past Due Accruing and Nonaccrual Loans	38,905	57,554
Consumer installment: | Nonperforming loans
Loans receivable
TDR loans	0	0
Other loans	159	217
Total Past Due Accruing and Nonaccrual Loans	$ 159	$ 217