LOANS - Loans by Class Modified as Troubled Debt Restructurings (Details) - Loans Excluding Purchased Loan $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2021 USD ($) contract branch	Mar. 31, 2020 USD ($) contract branch	Dec. 31, 2020 USD ($) contract
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	11	10
Troubled debt restructurings principal balances	$ 8,693	$ 976
Financing Receivables, 30 Days Past Due
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	38	24
Troubled debt restructurings principal balances	$ 6,159	$ 2,968
Financing Receivables, 30 Days Past Due | Accruing Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	682		752
Troubled debt restructurings principal balances	$ 80,111		$ 78,843
Financing Receivables, 30 Days Past Due | Non-Accruing Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	132		128
Troubled debt restructurings principal balances	$ 6,985		$ 6,145
Commercial, financial and agricultural
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	4	0
Troubled debt restructurings principal balances	$ 463	$ 0
Commercial, financial and agricultural | Financing Receivables, 30 Days Past Due
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	3	1
Troubled debt restructurings principal balances	$ 56	$ 200
Commercial, financial and agricultural | Financing Receivables, 30 Days Past Due | Accruing Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	10		9
Troubled debt restructurings principal balances	$ 930		$ 521
Commercial, financial and agricultural | Financing Receivables, 30 Days Past Due | Non-Accruing Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	12		11
Troubled debt restructurings principal balances	$ 854		$ 849
Consumer installment
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	0	1
Troubled debt restructurings principal balances	$ 0	$ 9
Consumer installment | Financing Receivables, 30 Days Past Due
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	5	0
Troubled debt restructurings principal balances	$ 6	$ 0
Consumer installment | Financing Receivables, 30 Days Past Due | Accruing Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	8		10
Troubled debt restructurings principal balances	$ 27		$ 32
Consumer installment | Financing Receivables, 30 Days Past Due | Non-Accruing Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	22		20
Troubled debt restructurings principal balances	$ 53		$ 56
Indirect automobile | Financing Receivables, 30 Days Past Due
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | branch	16	0
Troubled debt restructurings principal balances	$ 94	$ 0
Indirect automobile | Financing Receivables, 30 Days Past Due | Accruing Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	385		437
Troubled debt restructurings principal balances	$ 1,931		$ 2,277
Indirect automobile | Financing Receivables, 30 Days Past Due | Non-Accruing Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	47		51
Troubled debt restructurings principal balances	$ 321		$ 461
Real estate – construction and development | Financing Receivables, 30 Days Past Due
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	1	2
Troubled debt restructurings principal balances	$ 1	$ 287
Real estate – construction and development | Financing Receivables, 30 Days Past Due | Accruing Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	4		4
Troubled debt restructurings principal balances	$ 501		$ 506
Real estate – construction and development | Financing Receivables, 30 Days Past Due | Non-Accruing Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	5		5
Troubled debt restructurings principal balances	$ 706		$ 707
Real estate – commercial and farmland
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	2	1
Troubled debt restructurings principal balances	$ 7,658	$ 64
Real estate – commercial and farmland | Financing Receivables, 30 Days Past Due
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	2	2
Troubled debt restructurings principal balances	$ 5,193	$ 681
Real estate – commercial and farmland | Financing Receivables, 30 Days Past Due | Accruing Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	27		28
Troubled debt restructurings principal balances	$ 43,398		$ 36,707
Real estate – commercial and farmland | Financing Receivables, 30 Days Past Due | Non-Accruing Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	10		7
Troubled debt restructurings principal balances	$ 2,233		$ 1,401
Real estate – residential
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	5	8
Troubled debt restructurings principal balances	$ 572	$ 903
Real estate – residential | Financing Receivables, 30 Days Past Due
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	11	19
Troubled debt restructurings principal balances	$ 809	$ 1,800
Real estate – residential | Financing Receivables, 30 Days Past Due | Accruing Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	248		264
Troubled debt restructurings principal balances	$ 33,324		$ 38,800
Real estate – residential | Financing Receivables, 30 Days Past Due | Non-Accruing Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of contracts | contract	36		34
Troubled debt restructurings principal balances	$ 2,818		$ 2,671